---
title: "21 in Roman numerals is XXI"
description: "21 in Roman numerals is XXI, written as 10 + 10 + 1. How it breaks down, how to write it, and the numbers either side."
url: https://atoneplace.net/roman-numerals/21/
site: "At One Place"
---

# 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

*XXI = 10 + 10 + 1 = 21*

| 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

- [19 in Roman numerals](https://atoneplace.net/roman-numerals/19/)
- [20 in Roman numerals](https://atoneplace.net/roman-numerals/20/)
- [22 in Roman numerals](https://atoneplace.net/roman-numerals/22/)
- [23 in Roman numerals](https://atoneplace.net/roman-numerals/23/)
- [4 in Roman numerals](https://atoneplace.net/roman-numerals/4/)
- [9 in Roman numerals](https://atoneplace.net/roman-numerals/9/)
- [14 in Roman numerals](https://atoneplace.net/roman-numerals/14/)
- [40 in Roman numerals](https://atoneplace.net/roman-numerals/40/)
- [42 in Roman numerals](https://atoneplace.net/roman-numerals/42/)
- [49 in Roman numerals](https://atoneplace.net/roman-numerals/49/)
- [50 in Roman numerals](https://atoneplace.net/roman-numerals/50/)
- [64 in Roman numerals](https://atoneplace.net/roman-numerals/64/)

## Sources

- Calculated on this page — At One Place (/about/)