What is the Greatest Common Factor of 639 and 645?

Greatest common factor (GCF) of 639 and 645 is 3.

GCF(639,645) = 3

We will now calculate the prime factors of 639 and 645, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 639 and 645.

How to find the GCF of 639 and 645?

We will first find the prime factorization of 639 and 645. After we will calculate the factors of 639 and 645 and find the biggest common factor number .

Step-1: Prime Factorization of 639

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

639 = 3² × 71¹

Step-2: Prime Factorization of 645

Prime factors of 645 are 3, 5, 43. Prime factorization of 645 in exponential form is:

645 = 3¹ × 5¹ × 43¹

Step-3: Factors of 639

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

1, 3, 9, 71, 213

Step-4: Factors of 645

List of positive integer factors of 645 that divides 639 without a remainder.

1, 3, 5, 15, 43, 129, 215

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 639 and 645. The biggest common factor number is the GCF number.
So the greatest common factor 639 and 645 is 3.

Also check out the Least Common Multiple of 639 and 645