What is a PRIME NUMBER?
A prime number can be divided, without a remainder, only by itself and by 1. For example, 17 can be divided only by 17 and by 1.
Also, 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, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, etc.
It is a number that cannot be divided by any whole number evenly except by 1 or itself.
1,2,3,5 are prime number
4,6,9 are not