What is the Greatest Common Factor of 399 and 405?

Greatest common factor (GCF) of 399 and 405 is 3.

GCF(399,405) = 3

We will now calculate the prime factors of 399 and 405, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 399 and 405.

How to find the GCF of 399 and 405?

We will first find the prime factorization of 399 and 405. After we will calculate the factors of 399 and 405 and find the biggest common factor number .

Step-1: Prime Factorization of 399

Prime factors of 399 are 3, 7, 19. Prime factorization of 399 in exponential form is:

399 = 3¹ × 7¹ × 19¹

Step-2: Prime Factorization of 405

Prime factors of 405 are 3, 5. Prime factorization of 405 in exponential form is:

405 = 3⁴ × 5¹

Step-3: Factors of 399

List of positive integer factors of 399 that divides 399 without a remainder.

1, 3, 7, 19, 21, 57, 133

Step-4: Factors of 405

List of positive integer factors of 405 that divides 399 without a remainder.

1, 3, 5, 9, 15, 27, 45, 81, 135

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 399 and 405. The biggest common factor number is the GCF number.
So the greatest common factor 399 and 405 is 3.

Also check out the Least Common Multiple of 399 and 405