Question

what would be a easier formula for Greatest Common Factor

Answer 1

Go online and search  "Euclid's algorithm".
It would teach you how to do it quickly.

Answer 2

The GCD is also known as the greatest common factor (gcf), highest common factor (hcf) greatest common measure (gcm) or highest common divisor.

This notion can be extended to polynomials (see Polynomial greatest common divisor) an