Question: what is the greatest common factor gcf of 6 and 15?
Answer: Greatest Common Factor of 6 and 15. Greatest common factor (GCF) of 6 and 15 is 3. We will now calculate the prime factors of 6 and 15, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 6 and 15.