21 in Words
How do you write 21 in words?
The number 21 is written twenty-one in words. As an ordinal it is twenty-first, and on a check you would write Twenty-one and 00/100.
Last updated 24 August 2026
Other ways to write it
| Cardinal | twenty-one |
|---|---|
| Ordinal | twenty-first |
| Currency | twenty-one dollars |
| Check format | Twenty-one and 00/100 |
How 21 is written
21 is the sum of its place values, 20 + 1, and is written twenty-one.
Its ordinal form is twenty-first — only the final element takes the ordinal ending — and on a check the amount line reads "Twenty-one and 00/100", where 00/100 stands for zero cents.
The hyphen in twenty-one is required: English hyphenates every compound number from twenty-one to ninety-nine.
For house-style rules on spelling out numbers, see the Chicago Manual of Style.
Facts about 21
- 21 is an odd number.
- It is not a prime number.
- Digit sum: 3.
- Roman numerals: XXI.
- Binary: 10101.
- Hexadecimal: 15.
| Digit | Place |
|---|---|
| 2 | tens |
| 1 | ones |
Try another number
Frequently asked questions
How do you write 21 in words?
21 in words is "twenty-one".
How do you spell 21?
21 is spelled "twenty-one".
How do you write 21 on a check?
On a check, write "Twenty-one and 00/100".