Count by 21 (Skip Counting by 21s)

Count by 21

Here we will show you how to count by 21, discuss counting by 21 patterns, and tell you why knowing how to count by 21 matters. To start off, note that Count by 21 means counting in 21s, or count by twenty-ones, and it is also called skip counting by 21.

How to count by 21
Normally, we would count by 1 like this: 1, 2, 3, 4, etc., but when we count by 21, we count 21, 42, 63, 84, and so on.

In other words, to count in intervals of 21 or skip counting by 21, we start with 21 and then add 21 to get the next number, and then continue adding 21 to the previous number to keep counting by 21, like this:

21
21 + 21 = 42
42 + 21 = 63
63 + 21 = 84
84 + 21 = 105
...

You can of course skip count by 21 forever, so it is impossible to make a list of all numbers, but below is a Count by 21 Chart of the first 100 numbers to get you started.

Looking at the chart above, you will see that the first column has the first ten numbers you get when you skip count by 21, the second column has the next ten numbers you get when you skip count by 21, and so forth.

Count by 21 Patterns
We organized the Skip Counting by 21s Chart above in 10 rows and 10 columns so you can easily identify patterns.

Skip counting always creates patterns. Figuring out these patterns may help you if want to count by 21, but don't have the Counting by 21s Chart above. Obviously, one pattern with counting by 21s is that the number increases by 21.

Furthermore, if you look at each row above, each number in the row has the same last digit (ones place). That means that every tenth number has the same last digit.

If you look down the columns, you will see that the last digit (ones place) repeats itself in blocks of 10 over and over. The pattern of the last digit when you count by 21 goes 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 and 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 and so on for as long as you count by 21.

Why Count by 21?
We think that understanding and learning about skip counting by 21 is important, because it teaches you how the arithmetic operations fit together. Below are some examples of what we mean.

When you count by twenty-one, you are also creating a list of multiples of 21 that you can use in math when you need the least common multiple. 21 times n equals the nth multiple or skip count of 21.

When you skip count by 21, you are also creating a list of numbers that 21 is divisible by. On top of that, skip counting by 21 is the same as making the 21 times table.

Skip Counting
Need to skip count by another number? Enter another number for us to skip count for you.

Count by 22
Here is the next number on our list that we used to skip count.