**In mathematics, a prime number is any whole number greater than one that has no positive factors other than one and itself.** For example, the number 17 is prime, because its only factors are one and 17.

Numbers with more than two positive factors are called composite numbers. For example, the number six is a composite number because it has the factors two and three in addition to one and six. All prime numbers greater than two are odd numbers, because all even numbers have two as a factor. Likewise, any prime number greater than five cannot end in the number five, because numbers ending in five have five as a factor.