21 in Roman Numerals
21 in Roman numerals is XXI. It is built from two parts: 20 + 1 = XX + I. Read it from left to right and add the values to get 21. Copy it below, see why it is written this way, and check the numbers before and after. The converter handles any number from 1 to 3,999.
21 in Roman numerals is XXI.
21 in Roman numerals: the breakdown
| Place value | Numeral | Value |
|---|---|---|
| 20 | XX | 20 |
| 1 | I | 1 |
| Total | XXI | 21 |
20 plus 1 is 21, so XX followed by I is XXI.
How to read XXI
- XX is 10 + 10, which is 20.
- I is 1.
- Add 20 + 1 to get 21.
The numbers around 21
Facts about 21
- 21 is an odd number.
- 21 is not prime: 21 = 3 x 7.
- The digits of 21 add up to 3.
- XXI is 3 letters long. It uses the symbols X and I.
Convert another number
21 = 20 + 1 = XX + I
What number is XXI?
XXI is the number 21. Reading it from left to right, XX is 20 and I is 1, which adds up to 21.
Questions and answers
What is 21 in Roman numerals?
21 in Roman numerals is XXI. It is made of two parts: 20 + 1 = XX + I. Read XXI from left to right, add the parts, and you get 21. Use the converter on this page to check any other number from 1 to 3,999.
How do you write 21 in Roman numerals?
Split 21 into its place values, write each one in Roman numerals, and join them from largest to smallest. For 21 that is 20 + 1, which is XX + I, so the answer is XXI. Check that no letter repeats more than three times in a row.
What number is XXI?
XXI is 21. Read it in place-value parts from left to right: XX is 20, I is 1. Add the parts to get 21. Letters after a larger or equal letter are added, and a smaller letter before a larger one is subtracted. You can also type XXI into the converter to read the number back.