What Is Prime Number?
A prime number is a whole number greater than 1 that can only be divided evenly by 1 and itself. Any number with more than two factors is called composite instead. Primes are the building blocks of every whole number, since every number greater than 1 can be broken down into a unique product of primes.
Example
7 is prime, since only 1 and 7 divide into it evenly. 8 is not prime, since 1, 2, 4, and 8 all divide into it.