# What is the lowest common multiple 84 and 54?

The least common multiple of the numbers 84 and 54 is
**756**.

### What is the HCM of 21 and 28?

The common multiples of 21 and 28 are 84, 168, 252, 336, ... and so on, never ending; so there is no real Highest Common Multiple. Do you mean: Highest Common Factor - the highest number which divides both 21 and 28 which is 7; or Lowest Common Multiple - the lowest number which is a multiple of both 21 and 28 which is 84.