# What is the HCF of 12, 15 and 21

HCF (Highest Common Factor) of two numbers is the largest possible number which divides the two numbers exactly without leaving any remainder.

## Answer: HCF of 12,15 and 21 is 3

HCF of 12,15 and 21 is the highest number that divides 12,15 and 21 exactly leaving the remainder 0.

## Explanation:

We will show two methods to find the highest common factor of 40, 42 and 45

### Method 1: HCF of 12,15 and 21 by Prime Factorization

Theprime factorization of 12,15 and 21 are listed below

Here, the common factor among the factors of 12,15 and 21 is 3

So, the highest common factor of (12,15 and 21) is 3

### Method 2: HCF of 12, 15, and 21 by Listing the Factors

Factors of 12 : 1, 2, 3, 4, 6, and 12

Factors of 15: 1, 3, 5 and 15

Factors of 21: 1, 3, 7 and 21

We see that only 1 and 3 are the only common factors among 12,15 and 21 and 3 being the biggest common factor.