# What is the Greatest Common Factor of 15 and 20?

Greatest common factor (GCF) of 15 and 20 is 5.

GCF(15,20) = 5

We will now calculate the prime factors of 15 and 20, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 15 and 20.

GCF Calculator and
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## How to find the GCF of 15 and 20?

We will first find the prime factorization of 15 and 20. After we will calculate the factors of 15 and 20 and find the biggest common factor number .

### Step-1: Prime Factorization of 15

Prime factors of 15 are 3, 5. Prime factorization of 15 in exponential form is:

15 = 31 × 51

### Step-2: Prime Factorization of 20

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

20 = 22 × 51

### Step-3: Factors of 15

List of positive integer factors of 15 that divides 15 without a remainder.

1, 3, 5

### Step-4: Factors of 20

List of positive integer factors of 20 that divides 15 without a remainder.

1, 2, 4, 5, 10

#### Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 15 and 20. The biggest common factor number is the GCF number.
So the greatest common factor 15 and 20 is 5.

Also check out the Least Common Multiple of 15 and 20