A positive integer (or "natural number") that is greater than 1 is called a prime number if it isn't a product of two smaller positive integer. If it is a product of smaller numbers, it is called a composite number. As an example, 13 is a prime number, but 14 is a composite number, since it is the product of the smaller numbers 2 and 7.

Prime Factorization

All composite numbers can be expressed as a multiplication of prime numbers. This is called its prime factorization. The divisors of a number are found through all unique combinations of its prime factors.