# Is 21 Divisible By 7?

In this quick and easy guide, we'll work out whether 21 is divisible by 7. 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 7". What we want to check is whether 21 can be divided by 7 without any remainder (i.e the answer is a whole number).

Checked whether 21 is divisible by 7 is a little more complicated and if you have a calculator it might be easier to skip ahead and just do the division and see if the answer is a whole number.

For those that want to learn, you can check if it is divisible by 7 by taking the last digit of 21, double it, and subtract it from the rest of the number. If the answer is divisible by 7 (including 0) then the number is also.

Let's calculate that now using the last digit, 1:

1 x 2 = 2

21 - 2 = 19

We can see that 19 IS divisible by 7, which means that 21 IS divisible by 7 too.

Another way you can figure out if 21 is divisible by 7 is by actually doing the calculation and dividing 21 by 7:

21 / 7 =   3

Since the answer to our division is a whole number, we know that 21 is divisible by 7.

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 7 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.