7 (number)

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7
Arabic Numeral 7
Ordinal 7th
seventh
Numeral system septenary
Factorization prime
Divisors 1, 7
Roman numeral VII
Roman numeral (Unicode) Ⅶ, ⅶ
Amharic
Indian ٧
Bengali
Chinese numeral 七,柒
Devanāgarī
Hebrew ז (Zayin)
Khmer
Thai
prefixes hepta-/hept- (from Greek) septua- (from Latin)
Binary 111
Octal 7
Duodecimal 7
Hexadecimal 7

7 (seven) is the natural number following 6 and preceding 8.

In mathematics

In numeral systems

Base Numeral system
2 binary 111
3 ternary 21
4 quaternary 13
5 quinary 12
6 senary 11
7 septenary 10
over 7 (octal, decimal, etc) 7

In quaternary, 7 is the smallest prime with a composite sum of digits.

In the English language, 7 is the only 2-syllable natural, positive 1-digit number

List of basic calculations

Multiplication 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 50 100 1000
7 times x 7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119 126 133 140 147 154 161 168 175 350 700 7000

Division 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15
7 div x 7 3.5 2.overline{3} 1.75 1.4 1.1overline{6} 1 0.875 0.overline{7} 0.7
0.overline{63} 0.58overline{3} 0.overline{538461} 0.5 0.4overline{6}
x div 7 0.overline{142857} 0.overline{285714} 0.overline{428571} 0.overline{571428} 0.overline{714285} 0.overline{857142} 1 1.overline{142857} 1.overline{285714} 1.overline{428571}
1.overline{571428} 1.overline{714285} 1.overline{857142} 2 2.overline{142857}

Exponentiation 1 2 3 4 5 6 7 8 9 10 11 12 13
7 ^ x, 7 49 343 2401 16807 117649 823543 5764801 40353607 282475249 1977326743 13841287201 96889010407
x ^ 7, 1 128 2187 16384 78125 279936 823543 2097152 4782969 10000000 19487171 35831808 62748517

Radix 1 5 10 15 20 25 30 40 50 60 70 80 90 100
110 120 130 140 150 200 250 500 1000 10000 100000 1000000
x_{7} 1 5 13_{7} 21_{7} 26_{7} 34_{7} 42_{7} 55_{7} 101_{7} 114_{7} 130_{7} 143_{7} 156_{7} 202_{7}
215_{7} 231_{7} 244_{7} 260_{7} 303_{7} 404_{7} 505_{7} 1313_{7} 2626_{7} 41104_{7} 564355_{7} 11333311_{7}

Evolution of the glyph

In the beginning, various Hindus wrote 7 more or less in one stroke as a curve that looks like an uppercase J upside down. The western Ghubar Arabs' main contribution was to make the longer line diagonal rather than straight, though they showed some tendencies to making the character more rectilinear. The eastern Arabs developed the character from a 6-look-alike into an uppercase V-look-alike. Both modern Arab forms influenced the European form, a two-stroke character consisting of a horizontal upper line joined at its right to a line going down to the bottom left corner, a line that is slightly curved in some font variants. As is the case with the European glyph, the Cham and Khmer glyph for 7 also evolved to look like their glyph for 1, though in a different way, so they were also concerned with making their 7 more different. For the Khmer this often involved adding a horizontal line above the glyph. This is analogous to the horizontal stroke through the middle that is sometimes used in handwriting in the Western world but which is almost never used in computer fonts. This horizontal stroke is, however, important to distinguish the glyph for seven from the glyph for one in writings that use a long upstroke in the glyph for one.

On the seven-segment displays of pocket calculators and digital watches, 7 is the number with the most common glyph variation (0, 6 and 9 also have variant glyphs). Most calculators use three line segments, but on Sharp, Casio, and a few other brands of calculators, 7 is written with four line segments. The reason is that in Japan & Korea 7 is written as ① in the illustration to the right.

While the shape of the 7 character has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender, as, for example, in .

Some people, especially in Eastern Europe and Latin America write 7 with a line in the middle and make the top line crooked

In science

  • The number of spots on a common ladybug.
  • With very few exceptions, all mammals' necks have seven bones.
  • ROY G. BIV = red, orange, yellow, green, blue, indigo, and violet were originally named as the seven colors of the rainbow, though blue and indigo are considered by some to be the same color.

Chemistry

Astronomy

In technology

In the classical world

In classical antiquity:

In religion

  • In Judaism:
    • A highly symbolic number in the Torah, alluding to the infusion of spirituality and Godliness into the Creation. For example:
    • God rested on and sanctified the seventh day (Sabbath).
    • A seven-day purification period is required for one who has become tamei to become tahor.
    • The Shemittah (Sabbatical) year arrives every seventh year.
    • The Jubilee (Yovel) year comes after 7 times 7 years.
    • The Counting of the Omer leading up to the Giving of the Torah is expressed as "7 times 7 weeks."
    • Shiv`a (another pronunciation of the Hebrew word for 7 -- ()), is the number of days of mourning. Hence, one sits Shiva. As in Shiva (Judaism)
    • The weekly Torah portion is divided into seven aliyahs, and seven men or boys over the age of 13 are called up for the reading of these aliyahs during Sabbath morning services.
    • Seven blessings are recited under the chuppah during a Jewish wedding ceremony.
    • A Jewish bride and groom are feted with seven days of festive meals after their wedding, known as Sheva Berachot ("Seven Blessings").
    • The number of Ushpizzin (also known as the "Seven Shepherds") who visit the sukkah during the holiday of Sukkot: Abraham, Isaac, Jacob, Joseph, Moses, Aaron, and David.
    • The number of nations God told the Israelites they would displace when they entered the land of Israel (Deut. 7:1): the Hittite, the Girgashite, the Amorite, the Canaanite, the Perizzite, the Hivite, and the Jebusite.
    • In Breslov tradition, the seven orifices of the face (2 eyes, 2 nostrils, 2 ears, and the mouth) are called "The Seven Candles."
    • The menorah (Hebrew: מנורה), is a seven branched candelabrum lit by olive oil in the Tabernacle and the Temple in Jerusalem. The menorah is one of the oldest symbols of the Jewish people. It is said to symbolize the burning bush as seen by Moses on Mount Sinai (Exodus 25).
    • The number of times Cain will be avenged by God if he is murdered (Gen 4:15).
    • The Israelites circled Jericho for 7 days and then the wall tumbled down.
  • In Christianity:
  • In Islam:
    • The number of ayat in surat al-Fatiha.
    • The number of heavens in Islamic tradition.
    • The number of Earths in Islamic tradition.
    • The number of circumambulations (Tawaf) that are made around the Kaaba
    • The number of walks {Al-Safa and Al-Marwah) that is travelling back and forth seven times during the ritual pilgrimages of Hajj and Umrah.
  • Others:
    • The number of Archangels according to some systems.
    • The minor symbol number of yang from the Taoist yin-yang.
    • The number of palms in an Egyptian Sacred Cubit.
    • The number of ranks in Mithraism.
    • The number seven is of particular significance within Cherokee cosmology.
    • In Buddhism, Buddha walked 7 steps at his birth.
  • In Hinduism:
    • The Sanskrit word 'sapta' refers to number seven.
    • The Indian Music has 'sapta swaras', means seven octats (sa re ga ma pa dha ni), which are basics of music, using which hundreds of Ragas are composed.
    • Celestial group of seven stars are named as 'Sapta Rishi' based on the seven great saints.
    • Seven Promises, Seven Rounds in Hindu Wedding and Seven Reincarnation
    • As per Hindu mythology, there are seven worlds in the universe, seven seas in the world and seven Rishies (seven gurus) called sapta rishis.
    • seven hills at tirumala also known as ezhu malaiyan means Sevenhills god

In mythology

  • In Khasi mythology, the seven divine women who were left behind on earth and became the ancestresses of all humankind.
  • The number of gateways traversed by Inanna during her descent into the underworld.
  • The number of sleeping men in the Christian myth of the "Seven Sleepers."
  • The Seven Sages in Sumerian mythology and various other mythologies.
  • The number of sages in Hindu mythology; their wives are the goddesses referred to as the "Seven Mothers."
  • The number of main islands of mythological Atlantis.
  • In Guaraní mythology, the number of prominent legendary monsters.
  • Seven Lucky Gods exist in Japanese mythology.
  • In British Folk lore, every 7 years the Fairy Queen pays a tithe to Hell (or possibly Hel) in the tale of Tam Lin.
  • In the British Folk tale of Thomas the Rhymer, he went to live in the faerie kingdom for 7 years.

In psychology

In music

In television

  • The name of one of the monsters in the cartoon television show Seven Little Monsters.
  • Seven, an episodic character from the sitcom Married... with Children.
  • In Star Trek: Voyager, Seven of Nine (also called Seven for short) is one of the crewmembers.
  • In an episode of Seinfeld entitled "The Seven", the name George Costanza desired to give his first-born (with Susan Ross) is "Seven;" he later falsely claimed that he had promised this to the widow of baseball great Mickey Mantle, whose uniform number was 7.
  • The name of a television show 7th Heaven.
  • Seven Network, a television network in Australia.
  • Maximum number of VHF broadcast channels available in any TV market in the United States of America; they are channels 2, 4, 5, 7, 9, 11, and 13 in the Greater New York City and Los Angeles-Long Beach SMSAs.
  • In Stargate SG-1 and Stargate Atlantis, most gate addresses use 7 chevrons on the gate.
  • Ultra Seven, a television series aired in 1967, and the superhero of the same name. He is the honorary seventh member of the Ultra Garrison.
  • The name of a memorable The Adventures of Super Mario Bros. 3 cartoon, 7 Continents for 7 Koopas.
  • In the anime series Fate/Stay Night and the Visual Novel of the same name, there are seven classes of servants: Saber, Archer, Lancer, Berserker, Rider, Assassin, and Caster.
  • Blake's Seven was a BBC Science Fiction series that ran from 1978 to 1981, often without Blake, or seven members of the crew.
  • In an episode of Friends, titled "The One With Phoebe's Uterus," when Chandler seeks advice from Monica and Rachel about how to get a girl to "agree" with him more(innuendo referring to how when his girlfriend dated Joey, during sex, Chandler constantly heard her yelling, "Yes!" etc.), Monica draws a woman and labels seven spots on the body that would increase her pleasure. Monica then says a combination that would work very well, ending with her saying, "4. 2. 2...4-7. 5-7. 6-7! 7!" repeating "7!" eight more times, sighing, fall back into the couch, then holding up a full hand and two fingers, silently mouthing the word, "seven..."

In film

In literature

In video games

  • 7 is a number used many times by Bungie Studios in their Halo series and Marathon trilogy. 7 appears in a variety of different contexts, from the stories of the games to the raw game coding. One obvious example is the fact that there are seven Halo rings strewn throughout the galaxy.
  • Final Fantasy VII has many instances of seven throughout the game and was even released (in North America) on the seventh day of September ("September" originally meant "seventh month") in 1997.
  • In the Sonic the Hedgehog games, Sonic collects seven Chaos Emeralds which allow him to turn into Super Sonic.
  • The number of individual personalities serving Harman Smith as part of the group of assassins called the Killer7, hence the title of the game.
  • In Kingdom Hearts there are seven Princesses of Heart (Snow White, Cinderella, Alice, Aurora, Belle, Jasmine, and Kairi (the only original character among them)). Seven (VII) is also the number of the character Saïx, a member of the antagonists Organisation XIII from Kingdom Hearts II.
  • In the Super Mario RPG/Paper Mario series of games, the collection of seven mystical items (predominantly stars, but also hearts in Super Paper Mario) is the main quest of the game.
  • In The Legend of Zelda: Ocarina of Time, the main quest involves awakening the seven sages of seven elements to banish evil from the land of Hyrule.
  • The number of Koopalings on Super Mario Bros. 3 and Super Mario World. It is also the number of worlds on Super Mario World, not counting the Star World or the Special course; and it is also the number of worlds on Super Mario Bros. 2.
  • The 7 is a group of deadly mercenaries that kidnap the protagonist's family in the video game Kane & Lynch: Dead Men.
  • In Final Fantasy X, there are seven main characters, each with a coresponding stellar naked eye celestial object which are used to unlock their most powerful weapons.
  • In the Ace Attorney Series, 7 is a recurring number. For example: There is a 7 year age gap between the main character and his assistant, there is a 7 year gap between the plots of Ace Attorney 3 and 4, the Chief of police, Gant's keycard number is 7777777.

In sports

In other fields

  • Seven is the number of external holes in the human head: two eyes, two nostrils, one mouth, two ears.
  • Seven is the smallest positive integer whose name in English is more than one syllable long.
  • The Kulin people of Australia living near the Dandenong Ranges traditionally have seven seasons. Some of the Native Americans of Montana also have seven seasons: chinook season, muddy spring, green summer, gold summer (or dry summer), 'Indian' Summer, late fall, and cold winter.
  • The United States Constitution, as drafted in Philadelphia in 1787, was composed of 7 Articles.
  • The United States declared Independence in the 7th month of 1776.
  • In a standard deck of playing cards the 7 of Diamonds is the only diamond card that can be viewed as upside down when reversed.
  • Lotto Super 7, a Canadian-lottery game

Seven is also:

Names and titles

  • Sevens, a card game.
  • An agency of photojournalists founded by seven photographers.
  • Canadian fashion photographer Sev Seven.
  • California graffiti artist Seven
  • In the Fushigi Yuugi series, the four beast gods each have seven warriors, the Genbu Seven, the Byakko Seven, the Seiryuu Seven, and the Suzaku Seven.
  • In the Catalan culture, seven is present in a lot of popular stories like "Les set cabretes i el llop".
  • Number 7 is a popular brand of Canadian cigarettes.
  • "The Seven", also written: "The Se7en" is an exclusive grouping of dental surgeons.
  • 7UP is the name of a popular soft drink.
  • 7-Eleven is the trading name of a chain of convenience stores based in the U.S.
  • Seven Jeans, also known as Seven '7' for all Mankind, a brand of designer jeans.
  • 7 (New York City Subway service), a service of the New York City Subway
  • 7-ip is the name of an Australian satellite and wireless technology start up
  • The Ultra Series has two heroes with "Seven" in their name: Ultra Seven and Ultra Seven-21.
  • SEVEN Networks is a US company producing mobile email software.
  • The circle 7 logo used by numerous ABC network O&O stations in the United States.
  • In a survey in England seven was discovered to be the most common lucky number in the 2000 people that were surveyed.

Notes

See also

References

  • Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987): 70 - 71

External links

ko:7 ja:7 th:7 zh-yue:7 zh:7

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Last updated on Thursday March 13, 2008 at 11:59:28 PDT (GMT -0700)
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