Question: what is the greatest common factor of the numbers 21 and 35?
Answer: Greatest Common Factor of 21 and 35. Greatest common factor (GCF) of 21 and 35 is 7. We will now calculate the prime factors of 21 and 35, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 21 and 35.