Question: what is the greatest common factor of the numbers 63 and 81?
Answer: Greatest Common Factor of 63 and 81. Greatest common factor (GCF) of 63 and 81 is 9. We will now calculate the prime factors of 63 and 81, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 63 and 81.