31 in Words
How do you write 31 in words?
The number 31 is written thirty one in words. As an ordinal it is thirty first, and on a check you would write Thirty one and 00/100.
Last updated 19 June 2026
Other ways to write it
| Cardinal | thirty one |
|---|---|
| Ordinal | thirty first |
| Currency | thirty one dollars |
| Check format | Thirty one and 00/100 |
How number-to-words spelling works
A cardinal number names a quantity (thirty one), while an ordinal names a position (thirty 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 31
- 31 is an odd number.
- It is a prime number.
- Digit sum: 4.
- Roman numerals: XXXI.
- Binary: 11111.
- Hexadecimal: 1F.
| Digit | Place |
|---|---|
| 3 | tens |
| 1 | ones |
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Frequently asked questions
How do you write 31 in words?
31 in words is "thirty one".
How do you spell 31?
31 is spelled "thirty one".
How do you write 31 on a check?
On a check, write "Thirty one and 00/100".