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 19 June 2026
Other ways to write it
| Cardinal | twenty one |
|---|---|
| Ordinal | twenty first |
| Currency | twenty one dollars |
| Check format | Twenty one and 00/100 |
How number-to-words spelling works
A cardinal number names a quantity (twenty one), while an ordinal names a position (twenty first). English hyphenates compound numbers from twenty-one to ninety-nine and groups digits into thousands, millions, and billions.
For house-style rules on spelling out numbers, see the Chicago Manual of Style, or read our guide to spelling numbers in words.
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 |
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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".