A prime number is a natural number greater than 1 that has exactly two factors, 1 and itself. In other words, a prime number is only divisible by 1 and itself. For example, 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29 are the first ten prime numbers. Numbers that have more than two factors are called composite numbers. The number 1 is neither prime nor composite. Prime numbers are important in mathematics and computer science, particularly in cryptography. There is no largest prime number, and as the set of natural numbers proceeds, prime numbers generally become less frequent and are more difficult to find in a reasonable amount of time.