One concept in math that is taught at the very early stages is the idea of a prime number. A prime number is a number that is divisible by only itself and the number one. The number 2, for example, is prime. The opposite of a prime number is a composite number. Composite numbers are divisible by multiple numbers. The number 50, for example, is prime. Use the program below to calculate all of the prime numbers within a range selected by you.