What is the Greatest Common Factor of 665 and 685?

Greatest common factor (GCF) of 665 and 685 is 5.

GCF(665,685) = 5

We will now calculate the prime factors of 665 and 685, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 665 and 685.

How to find the GCF of 665 and 685?

We will first find the prime factorization of 665 and 685. After we will calculate the factors of 665 and 685 and find the biggest common factor number .

Step-1: Prime Factorization of 665

Prime factors of 665 are 5, 7, 19. Prime factorization of 665 in exponential form is:

665 = 5¹ × 7¹ × 19¹

Step-2: Prime Factorization of 685

Prime factors of 685 are 5, 137. Prime factorization of 685 in exponential form is:

685 = 5¹ × 137¹

Step-3: Factors of 665

List of positive integer factors of 665 that divides 665 without a remainder.

1, 5, 7, 19, 35, 95, 133

Step-4: Factors of 685

List of positive integer factors of 685 that divides 665 without a remainder.

1, 5, 137

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 665 and 685. The biggest common factor number is the GCF number.
So the greatest common factor 665 and 685 is 5.

Also check out the Least Common Multiple of 665 and 685