# What is the LCM of 15 and 21?

The least common multiple can be defined as the lowest positive integer that is a multiple of every number in a given set of numbers.

## Answer: LCM of 15 and 21 is 105

Lets see how to find the LCM of 15 and 21

## Explanation:

We will be calculating the LCM in two ways:

- Prime factorization
- Using Formula

### LCM of 15 and 21 using Prime Factorization:

We will be prime factorising the numbers 15 and 21 as shown below

### LCM by using formula:

LCM (a, b) = (a × b) / GCF (a, b)

The Greatest Common Factor of (15,21) = 3

Therefore by substituting we get,

LCM of 15 and 21 = (15 × 21) / 3

= 105

LCM of 15 and 21 = 105