# What is the Greatest Common Factor of 78 and 87?

Greatest common factor (GCF) of 78 and 87 is **3**.

GCF(78,87) = 3

We will now calculate the prime factors of **78 and 87**, than find the greatest common factor *(greatest common divisor (gcd))* of the numbers by matching the biggest common factor of 78 and 87.

## How to find the GCF of 78 and 87?

We will first find the prime factorization of 78 and 87. After we will calculate the factors of 78 and 87 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 87

Prime factors of 87 are 3, 29. Prime factorization of **87** in exponential form is:

87 = 3^{1} × 29^{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 87

List of positive integer factors of 87 that divides 78 without a remainder.

1, 3, 29

#### Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 78 and 87. The biggest common factor number is the **GCF** number.

So the **greatest common factor 78 and 87** is **3**.

Also check out the Least Common Multiple of 78 and 87