Question: what is the greatest common factor gcf of 12 and 40?
Answer: Greatest Common Factor of 12 and 40. Greatest common factor (GCF) of 12 and 40 is 4. We will now calculate the prime factors of 12 and 40, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 12 and 40.