# What is the Greatest Common Factor of 72 and 81?

Greatest common factor (GCF) of 72 and 81 is 9.

GCF(72,81) = 9

We will now calculate the prime factors of 72 and 81, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 72 and 81.

GCF Calculator and
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## How to find the GCF of 72 and 81?

We will first find the prime factorization of 72 and 81. After we will calculate the factors of 72 and 81 and find the biggest common factor number .

### Step-1: Prime Factorization of 72

Prime factors of 72 are 2, 3. Prime factorization of 72 in exponential form is:

72 = 23 × 32

### Step-2: Prime Factorization of 81

Prime factors of 81 are 3. Prime factorization of 81 in exponential form is:

81 = 34

### Step-3: Factors of 72

List of positive integer factors of 72 that divides 72 without a remainder.

1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36

### Step-4: Factors of 81

List of positive integer factors of 81 that divides 72 without a remainder.

1, 3, 9, 27

#### Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 72 and 81. The biggest common factor number is the GCF number.
So the greatest common factor 72 and 81 is 9.

Also check out the Least Common Multiple of 72 and 81