# What is the Greatest Common Factor of 78 and 91?

Greatest common factor (GCF) of 78 and 91 is **13**.

GCF(78,91) = 13

We will now calculate the prime factors of **78 and 91**, than find the greatest common factor *(greatest common divisor (gcd))* of the numbers by matching the biggest common factor of 78 and 91.

## How to find the GCF of 78 and 91?

We will first find the prime factorization of 78 and 91. After we will calculate the factors of 78 and 91 and find the biggest common factor number .

### Step-1: Prime Factorization of 78

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

78 = 2^{1} × 3^{1} × 13^{1}

### Step-2: Prime Factorization of 91

Prime factors of 91 are 7, 13. Prime factorization of **91** in exponential form is:

91 = 7^{1} × 13^{1}

### Step-3: Factors of 78

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

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

### Step-4: Factors of 91

List of positive integer factors of 91 that divides 78 without a remainder.

1, 7, 13

#### Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 78 and 91. The biggest common factor number is the **GCF** number.

So the **greatest common factor 78 and 91** is **13**.

Also check out the Least Common Multiple of 78 and 91

#### Related Greatest Common Factors of 78

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