Prime numbers are defined as numbers greater than one that can be divided only by one and itself.
It is helpful to know the prime numbers under 100, which are:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97