# Is 21 Divisible By 8?

In this quick and easy guide, we'll work out whether 21 is divisible by 8. There are some simple rules we can follow to decide whether one number is divisible by another without ever needing to even do the division!

First up, let's clarify what we mean by "21 is divisible by 8". What we want to check is whether 21 can be divided by 8 without any remainder (i.e the answer is a whole number).

With smaller numbers, checking divisibility by 8 is easiest by just mentally doing your 8 times table and seeing if 21 is part of it. For larger numbers, you can take the last 3 digits and check whether that number (in this case 21) is divisible by 8. If it is, then 21 is too.

In this case, we can see that 21 IS NOT divisible by 8, which means that 21 IS NOT divisible by 8 either.

Another way you can figure out if 21 is divisible by 8 is by actually doing the calculation and dividing 21 by 8:

21 / 8 =   2.625

As you can see, when we do this division we have a decimal of 0.625. Since the division does not result in a whole number, this shows us that 21 is not divisible by 8.

Hopefully now you know exactly how to work out whether one number is divisible by another. Could I have just told you to divide 21 by 8 and check if it is a whole number? Yes, but aren't you glad you learned the process?

Give this a go for yourself and try to calculate a couple of these without using our calculator. Grab a pencil and a piece of paper and pick a couple of numbers to try it with.