21 in Roman numerals
Roman numeral
XXI
How XXI is built
Read left to right, adding as you go; a smaller letter in front of a larger one is taken away instead, which is what the two-letter pieces below are. The rules in full, and the mistakes they prevent.
| Piece | Value | Running total |
|---|---|---|
| X | 10 | 10 |
| X | 10 | 20 |
| I | 1 | 21 |
21 in other forms
- Roman numeral
- XXI
- In figures
- 21
- In words
- twenty-one
- Letters used
- 3 letters