# What is the Greatest Common Factor of 66 and 78?

Greatest common factor (GCF) of 66 and 78 is 6.

GCF(66,78) = 6

We will now calculate the prime factors of 66 and 78, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 66 and 78.

GCF Calculator and
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## How to find the GCF of 66 and 78?

We will first find the prime factorization of 66 and 78. After we will calculate the factors of 66 and 78 and find the biggest common factor number .

### Step-1: Prime Factorization of 66

Prime factors of 66 are 2, 3, 11. Prime factorization of 66 in exponential form is:

66 = 21 × 31 × 111

### Step-2: Prime Factorization of 78

Prime factors of 78 are 2, 3, 13. Prime factorization of 78 in exponential form is:

78 = 21 × 31 × 131

### Step-3: Factors of 66

List of positive integer factors of 66 that divides 66 without a remainder.

1, 2, 3, 6, 11, 22, 33

### Step-4: Factors of 78

List of positive integer factors of 78 that divides 66 without a remainder.

1, 2, 3, 6, 13, 26, 39

#### Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 66 and 78. The biggest common factor number is the GCF number.
So the greatest common factor 66 and 78 is 6.

Also check out the Least Common Multiple of 66 and 78