A counting number (n) is called a prime
number if it has exactly two factors (n = n&nbsp; x 1), namely itself (n) and 1. Ex. All prime
numbers less than 100 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.