Two natural numbers are called COPRIME, or relatively prime, if and only if they have no common divisor other than 1, or, equivalently, if their greatest common divisor is 1.

For example:
6 and 35 are coprime, but 6 and 27 are not because both are divisible by 3.

A good way to determine if two numbers are coprime is given by the Euclidean algorithm.

PROPERTIES

The natural numbers a and b are coprime if and only if x e y integers exist so that ax+by=1.

If a and b are coprime and a divides a product bc, then a divides c.

Two numbers a and b are coprime if and only if the point with coordinates (a,b) in a Cartesian coordinate system is "visible" from the origin (0,0), in the sense that there is no point with integer coordinates between the origin and the point (a,b).