What is the Greatest Common Factor of 621 and 639?

Greatest common factor (GCF) of 621 and 639 is 9.

GCF(621,639) = 9

We will now calculate the prime factors of 621 and 639, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 621 and 639.

How to find the GCF of 621 and 639?

We will first find the prime factorization of 621 and 639. After we will calculate the factors of 621 and 639 and find the biggest common factor number .

Step-1: Prime Factorization of 621

Prime factors of 621 are 3, 23. Prime factorization of 621 in exponential form is:

621 = 3³ × 23¹

Step-2: Prime Factorization of 639

Prime factors of 639 are 3, 71. Prime factorization of 639 in exponential form is:

639 = 3² × 71¹

Step-3: Factors of 621

List of positive integer factors of 621 that divides 621 without a remainder.

1, 3, 9, 23, 27, 69, 207

Step-4: Factors of 639

List of positive integer factors of 639 that divides 621 without a remainder.

1, 3, 9, 71, 213

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 621 and 639. The biggest common factor number is the GCF number.
So the greatest common factor 621 and 639 is 9.

Also check out the Least Common Multiple of 621 and 639