What is the greatest common factor of 126 and 189?

The GCF of 126 and 189 is 63.

The easiest way to solve this is by breaking down 126 and 189 into a series of prime numbers multiplied together. 126 = 2*(3^2)*7, and 189 = (3^3)*7

So taking the minimum powers on each side will give you the GCF.

Thus GCD(126,189) = (2^0)*(3^2)*(7^1)= 1*9*7 = 63.