21 in Roman numerals
21 in Roman numerals
XXI
21 is written XXI in Roman numerals. That is 3 symbol groups added together, reading left to right from the largest value down.
How it breaks down
| Group | Value | Subtraction | Running total |
|---|---|---|---|
| X | 10 | — | 10 |
| X | 10 | — | 20 |
| I | 1 | — | 21 |
No subtraction needed
XXI is purely additive — every symbol is simply added to the one before it, with no subtractive pairs like IV or IX. Numbers avoid subtraction when none of their digits is a 4 or a 9.
The symbols
| Symbol | Value | Used here |
|---|---|---|
| I | 1 | yes — 1× |
| V | 5 | no |
| X | 10 | yes — 2× |
| L | 50 | no |
| C | 100 | no |
| D | 500 | no |
| M | 1,000 | no |
The same number, other ways
- In words
- Twenty-one
- Roman numeral
- XXI
- Symbol count
- 3 characters
- Binary
- 10101
- Hexadecimal
- 15
The numbers either side
| Number | Roman numeral |
|---|---|
| 19 | XIX |
| 20 | XX |
| 21 | XXI ← |
| 22 | XXII |
| 23 | XXIII |
Common questions
- What is 21 in Roman numerals?
- 21 is XXI.
- What does XXI mean?
- XXI is the Roman numeral for 21 — 10 + 10 + 1.
- How do you write 21 in Roman numerals?
- Take the largest value that fits and repeat until nothing is left: X (10), then X (10), then I (1). That gives XXI.
Related pages
Sources
- Calculated on this page — At One Place