21 in Roman Numerals
21 written in Roman numeralsXXI
21 = XXI. Read left to right: XX (20) + I (1) = 21.
Going the other way, the Roman numeral XXI equals the number 21.
How to write 21 in Roman numerals
- Tens: 20 is XX.
- Ones: 1 is I.
- Put them together, largest first: XX + I = XXI.
XXI uses only additive notation: every symbol is the same size or smaller than the one before it, so you simply add them up.
21 is an odd number and written with 3 symbols in Roman numerals.
Where you might see XXI
- In dates written in Roman numerals, XXI can stand for day 21 of the month.
- Super Bowl XXI was the 21st Super Bowl, played in early 1987.
- Book chapters, outlines, movie sequels and royal names use numerals like XXI for the number 21.
Multiples of XXI
| Sum | Number | Roman numeral |
|---|---|---|
| 21 × 2 | 42 | XLII |
| 21 × 3 | 63 | LXIII |
| 21 × 5 | 105 | CV |
| 21 × 10 | 210 | CCX |
Numerals near XXI
| Number | Roman numeral |
|---|---|
| 16 | XVI |
| 17 | XVII |
| 18 | XVIII |
| 19 | XIX |
| 20 | XX |
| 21 | XXI |
| 22 | XXII |
| 23 | XXIII |
| 24 | XXIV |
| 25 | XXV |
| 26 | XXVI |
Questions
How do you write 21 in Roman numerals?
21 is written XXI.
What number is XXI?
XXI is 21.