Coprime

The integers a and b are said to be coprime or relatively prime iff they have no common factor other than 1 and -1. (In particular, 1 is coprime to every integer; 0 is coprime only to 1 and -1.) For example, 6 and 35 are coprime, but 6 and 28 are not.

In other words, a and b are coprime iff their greatest common divisor is 1.

This is equivalent to the existence of integers p and q such that ap + bq = 1.