# What is the Greatest Common Factor of 28 and 40?

Greatest common factor (GCF) of 28 and 40 is 4.

GCF(28,40) = 4

We will now calculate the prime factors of 28 and 40, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 28 and 40.

GCF Calculator and
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## How to find the GCF of 28 and 40?

We will first find the prime factorization of 28 and 40. After we will calculate the factors of 28 and 40 and find the biggest common factor number .

### Step-1: Prime Factorization of 28

Prime factors of 28 are 2, 7. Prime factorization of 28 in exponential form is:

28 = 22 × 71

### Step-2: Prime Factorization of 40

Prime factors of 40 are 2, 5. Prime factorization of 40 in exponential form is:

40 = 23 × 51

### Step-3: Factors of 28

List of positive integer factors of 28 that divides 28 without a remainder.

1, 2, 4, 7, 14

### Step-4: Factors of 40

List of positive integer factors of 40 that divides 28 without a remainder.

1, 2, 4, 5, 8, 10, 20

#### Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 28 and 40. The biggest common factor number is the GCF number.
So the greatest common factor 28 and 40 is 4.

Also check out the Least Common Multiple of 28 and 40