Board Thread:Off Topic/@comment-26446727-20161110233310/@comment-26446727-20161111020647

M9, there are two integers that are neither prime nor composite, 1 and 0. Negative numbers are never included.

If negative numbers were included, no number would be prime, as 2 would have four factors, 2, -1, -2, and 1. Therefore, negative numbers are irrelevant in primeness.

10.