What is the Greatest Common Factor of 20 and 405?

Greatest common factor (GCF) of 20 and 405 is 5.

GCF(20,405) = 5

We will now calculate the prime factors of 20 and 405, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 20 and 405.

How to find the GCF of 20 and 405?

We will first find the prime factorization of 20 and 405. After we will calculate the factors of 20 and 405 and find the biggest common factor number .

Step-1: Prime Factorization of 20

Prime factors of 20 are 2, 5. Prime factorization of 20 in exponential form is:

20 = 2² × 5¹

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 20

List of positive integer factors of 20 that divides 20 without a remainder.

1, 2, 4, 5, 10

Step-4: Factors of 405

List of positive integer factors of 405 that divides 20 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 20 and 405. The biggest common factor number is the GCF number.
So the greatest common factor 20 and 405 is 5.

Also check out the Least Common Multiple of 20 and 405