I was going to try to do this (convert definition of a prime number to a mathematical expression) but, not being a mathematician, I wanted to check and see if I was thinking about this the wrong way.

The converse tells us what we expect for small non-prime numbers as well. If we use it to check whether 4 is prime or not, we’ll compute 24– 2 and observe that 14 is not divisible by 4. In fact, you ...