# What is the GCF of 18 and 81?

Greatest common factor or highest common factor is the largest number that divides the two given numbers.

## Answer: The GCF of 18 and 81 is 9

Let us see how to find the GCF of 18 and 81

## Explanation:

We will be finding the prime factors of 18 and 81

GCF will be the product of all the common prime factors of 18 and 81

GCF(18,81) = 3 × 3 = 9

Let's look into the long division method to calculate the GCF

- Divide the larger number by the smaller number.
- Now divide the divisor by the remainder.
- Repeat the process of dividing the preceding number by the remainder last until 0 zero is obtained as remainder.
- The last divisor is called GCF

Thus, the GCF of 18 and 81 will be 9