10 (ten) is an even natural number following 9 and preceding 11.

In mathematics

Ten is a composite number, its proper divisors being 1, 2 and 5. Ten is the smallest noncototient, a number that can not be expressed as the difference between any integer and the total number of coprimes below it.

Ten is the second discrete biprime (2.5) and the second member of the (2.q) discrete biprime family. Ten has an aliquot sum σ(n) of 8 and is accordingly the first discrete biprime to be in deficit. All subsequent discrete biprimes are in deficit. The aliquot sequence for 10 comprises five members (10,8,7,1,0) with this number being the second composite member of the 7-aliquot tree.

It is the aliquot sum of only one number the discrete biprime 14.

Ten is a semi-meandric number.

Ten is the sum of the first three prime numbers and also of the first four factorials. Ten is the eighth Perrin number, preceded in the sequence by 5, 5, 7.

Ten squared equals 100.

A polygon with ten sides is a decagon, and 10 is a decagonal number. But it is also a triangular number and a centered triangular number.

Ten is the number of n-Queens Problem solutions for n = 5.

In numeral systems

Ten is the base of the decimal numeral system, by far the most common system of denoting numbers in both spoken and written language. Ten is the first two-digit number in decimal and thus the lowest number where the position of a numeral affects its value. Any integer written in the decimal system can be multiplied by ten by adding a zero to the end (e.g. 855 * 10 = 8550). The reason for the choice of ten is assumed to be that humans have ten fingers (digits).

The digit '1' followed by '0' is how the value of p is written in base p. (E.g. 16 in hexadecimal is 10.)

The Roman numeral for ten is X (which looks like two V's [the Roman numeral for 5] put together); it is thought that the V for five is derived from an open hand (five digits displayed). The Chinese word numeral for ten is 十, which resembles a cross.

Base	Numeral system	Number
1	unary	**********
2	binary	1010
3	ternary	101
4	quaternary	22
5	quinary	20
6	senary	14
7	septenary	13
8	octal	12
9	novenary	11
10	decimal	10
over 10 (e.g., hexadecimal)		A

Ten is a Harshad number in bases 2, 3, 5, 6, 9 and all others above.

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	25		50	100	1000
$10\; times\; x$	10	20	30	40	50	60	70	80	90	100		110	120	130	140	150	160	170	180	190	200		210	220	250		500	1000	10000

Division	1	2	3	4	5	6	7	8	9	10		11	12	13	14	15
$10\; div\; x$	10	5	$3.overline\{3\}$	2.5	2	$1.overline\{6\}$	$1.overline\{4\}2857overline\{1\}$	1.25	$1.overline\{1\}$	1		$0.overline\{9\}overline\{0\}$	$0.8overline\{3\}$	$0.overline\{7\}6923overline\{0\}$	$0.overline\{7\}1428overline\{5\}$	$0.overline\{6\}$
$x\; div\; 10$	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1		1.1	1.2	1.3	1.4	1.5

Exponentiation	1	2	3	4	5	6	7	8	9	10		11	12	13
$10\; ^\; x,$	10	100	1000	10000	100000	1000000	10000000	100000000	1000000000	10000000000		100000000000	1000000000000	10000000000000
$x\; ^\; \{10\},$	1	1024	59049	1048576	9765625	60466176	282475249	1073741824	3486784401	10000000000		25937424601	61917364224	137858491849

In science

• The atomic number of neon
• The number of carbon atoms in decane, a hydrocarbon.
• The number of spacetime dimensions in some superstring theories.

Astronomy

• Messier object M10, a magnitude 7.5 globular cluster in the constellation Ophiuchus.
• The New General Catalogue object NGC 10, a magnitude 12.5 spiral galaxy in the constellation Sculptor
• The Saros number of the solar eclipse series which began on -2467 February 28 and ended on -1169 April 18. The duration of Saros series 10 was 1298.1 years, and it contained 73 solar eclipses.
• The Saros number of the lunar eclipse series which began on -2454 June 17 and ended on -1138 August 15. The duration of Saros series 10 was 1316.2 years, and it contained 74 lunar eclipses.

In religion

• The Ten Commandments of and are considered a cornerstone of Judaism and Christianity.
• People traditionally tithed one-tenth of their produce. The practice of tithing is still common in Christian churches today, though it is disputed in some circles as to whether or not it is required of Christians.
• In Deuteronomy 26:12, the Torah commands Jews to give one-tenth of their produce to the poor (Maaser Ani). From this verse and from an earlier verse (Deut. 14:22) there derives a practice for Jews to give one-tenth of all earnings to the poor
• Ten Plagues were inflicted on Egypt in
• Jews observe the annual Ten Days of Repentance beginning on Rosh Hashanah and ending on Yom Kippur.
• In Jewish liturgy, Ten Martyrs are singled out as a group.
• There are said to be Ten Lost Tribes of Israel (those other than Judah and Benjamin)
• There are Ten Sephirot in the Kabbalistic Tree of Life
• The Bible records 10 generations between Adam and Noah, and 10 generations between Noah and Abraham
• In Judaism, ten adults are the required quorum for prayer services.

In money

• There are ten cents in a U.S. or Canadian dime, itself one tenth of a dollar. The word was shortened from decime.
• The denomination of Canadian paper money bearing a portrait of Sir John A. Macdonald, Canada's first Prime Minister.

In music

• The interval of a major or minor tenth is an octave plus a major or minor third.
• The title of quite a few albums, including recordings by Pearl Jam and LL Cool J. See Ten (album).

In sports

• In rugby union the fly-half wears the 10 shirt.
• In blackjack, the Ten, Jack, Queen and King are all worth 10 points.
• In ten-pin bowling 10 pins are arranged in a triangular pattern and there are 10 frames per game.
• In football (soccer), the jersey number of many of the best players, particularly attacking midfielders, especially players from South America. Football legend Pelé instilled great prestige in the number in the 1960s and 70s. Other legends to have worn the number are Michel Platini, Zico, Diego Maradona, Lothar Matthäus, Gary Lineker, Roberto Baggio, Zinedine Zidane, Rivaldo, Ronaldinho, Dennis Bergkamp, Michael Owen, Juan Román Riquelme, Rui Costa, Francesco Totti, Denis Law, Gheorghe Hagi, Zvonimir Boban, William Gallas, Zlatan Ibrahimovic, and Michelle Akers, Wayne Rooney (the shirt was also worn by David Beckham during the 1996/97 season). For the 2002 World Cup Argentina requested to have the number 10 'retired' from their squad list and replaced by 24 in honour of Diego Maradona. FIFA rejected this request saying that Argentina could only leave 10 off the squad list if they intended to enter a squad of 22 players rather than the permitted 23. Argentina decided to bring 23 players to Japan & Korea with Ariel Ortega given the coveted 10. 'Number 10' player is most often used as a synonym for the team's playmaker.
• The highest score possible in Olympics competitions.
• In cricket, 10 is the number of wickets required to be taken by the bowling side for the batting side to be bowled out
• In Australian rules football, considered the break even amount of games won in a regular 22 game season, especially by Richmond coach Terry Wallace.
• In Baseball there are always at least 10 players on the field at a time (including the batter).
• The number of Baseball Hall of Famer and former New York Yankees Shortstop Phil Rizzuto
• The number of the Boston Red Sox amazing center fielder Coco(Corvellie)Crisp.
• The NASCAR car number of Scott Riggs
• Eli Manning New York Giants wears #10
• Brady Quinn Cleveland Browns wears #10
• Vince Young Tennessee Titans Wears #10

In technology

• Driving a racing car at ten-tenths is driving as fast as possible, on the limit.
• Ten-codes are commonly used on emergency service radio systems.
• Ten refers to the "meter band" on the radio spectrum between 28 and 29.7 MHz, used by amateur radio.
• ASCII and Unicode code point for line feed
• In MIDI, Channel 10 is reserved for unpitched percussion instruments.
• In the Rich Text Format specification, all language codes for regional variants of the Spanish language are congruent to 10 mod 256.
• In Mac OS X, the F10 function key tiles all the windows of the current application and grays the windows of other applications.
• The IP addresses in the range 10.0.0.0/8 (meaning the interval between 10.0.0.0 and 10.255.255.255) is reserved for use by Private networks by RFC 1918.

Age 10

• Minimum age at which can watch a TV-PG show without parental consent.
• Minimum age at which can watch a 10-rated show or movie in Brazil without parental consent.
• Minimum age at which can rent, buy or play a E10+ rated game by the ESRB without parental consent.

In other fields

• Number of incarnations of The Doctor in the BBC science fiction television program Doctor Who
• Increasing a quantity by one order of magnitude is most widely understood to mean multiplying the quantity by ten.
• The number of theatrical Star Trek films that have been released so far.
• A collection of ten items (most often ten years) is called a decade.
• A decapod crustacean has ten limbs.
• To reduce something by one-tenth is to decimate. (In ancient Rome, the killing of one in ten soldiers in a cohort was the punishment for cowardice or mutiny; or, one-tenth of the able-bodied men in a village as a form of retribution, thus causing a labor shortage and threat of starvation in agrarian societies.)
• With ten being the base of the decimal system, a scale of 1 to 10 is often used to rank things, as a smaller version of a 1-to-100 scale (as is used in percentages and wine-tasting).
• Blake Edwards' 1979 movie 10.
• Something that scores perfectly is "a perfect ten". A person who is attractive and physically flawless is often said to be "a ten", from the idea of ranking that person's appearance and sex-appeal on a 1-to-10 scale. For example, in the movie 10 Bo Derek is supposedly a "10" on that scale.
• Counting from one to ten before speaking is often done in order to cool one's temper.
• In astrology, Capricorn is the 10th astrological sign of the Zodiac.
• In Chinese astrology, the 10 Heavenly Stems, refer to a cyclic number system that is used also for time reckoning.
• The ordinal adjective is denary.
• An online show hosted by Microsoft.
• Ben 10 is a show about a boy that can transform into 10 aliens.
• A 1977 short documentary film Powers of Ten depicts the relative scale of the Universe in factors of ten (orders of magnitude).
• CBS has a game show called Power of 10, where the player's prize goes up and down by either the previous or next power of ten.
• There are ten official inkblots in the Rorschach inkblot test.
• The traditional Snellen chart uses 10 different letters.

Ten is:

• Number of kingdoms in Five Dynasties and Ten Kingdoms Period
• House number of 10 Downing Street
• The number of Provinces in Canada
• The designation of United States Interstate 10, a freeway that runs from California to Florida.
• A Japanese comic: Ten (comic)
• Number of dots in a tetractys.
• The number of the French department Aube

Historical years

10 A.D., 10 B.C., 1910, 2010, etc.

See also