## Coprime numbers (numbers prime to each other, relatively prime, mutually prime)

#### Integers "a" and "b" are said to be relatively prime, mutually prime, or coprime if the only positive integer that divides both of them is 1. This is equivalent to their only common positive factor being 1. This is also equivalent to their greatest common factor (divisor) being 1.

For example, 16 and 17 are coprime, being commonly divisible by only 1, but 16 and 24 are not, because they are both divisible by 8. The numbers 1 and -1 are the only integers coprime to every integer, and they are the only integers to be coprime with 0. A fast way to determine whether two numbers are coprime is given by the Euclidean algorithm: Euclid's algorithm