21 in Roman numerals is XXI, built from XX + I (XX = 20, I = 1), which add up to 21.
How 21 is written in Roman numerals
The number 21 is written XXI in Roman numerals. Roman numerals use seven letters — I (1), V (5), X (10), L (50), C (100), D (500) and M (1000) — combined from largest to smallest, with subtractive pairs such as IV (4) and IX (9). Need another number? Use the Roman numeral converter or see the 1–100 chart.
Building XXI step by step — take the largest value that fits, write its symbol, subtract, repeat.
| Write | Value | Remaining before | Remaining after |
|---|
| X | 10 | 21 | 11 |
| X | 10 | 11 | 1 |
| I | 1 | 1 | 0 |
Where you see XXI
Regnal and papal names use it the same way — a 21st ruler of a name is styled XXI, as in Louis XXI or Pope John XXI. The 21st Super Bowl was Super Bowl XXI; the NFL has used Roman numerals for every edition except Super Bowl 50.
Nearby numbers
Popular numbers in Roman numerals
Frequently Asked Questions
What is 21 in Roman numerals?
21 in Roman numerals is XXI. Reading it left to right gives X (10) + X (10) + I (1) = 21. The number below it, 20, is written XX, and the number above it, 22, is written XXII.
How do you write 21 in Roman numerals?
Write 21 as XXI, combining X (10) + X (10) + I (1). Roman numerals are built by taking the largest value that still fits, writing its symbol and subtracting it, which reduces 21 in 3 steps: X leaves 11, X leaves 1, I leaves 0. Every symbol keeps the same value wherever it stands, so the order is fixed and XXI is the only standard spelling of 21.
Which letters make up XXI?
XXI is made up of X twice and I once. X is worth 10 and I is worth 1. Added together those values come to 21, because Roman numerals are read by summing the symbols from left to right.
What is 21 times ten in Roman numerals?
21 times ten is 210, which is CCX in Roman numerals, not XXI with a letter added on the end. Roman numerals have no place value, so multiplying by ten respells the whole numeral instead of shifting digits along. Compare XXI for 21 with CCX for 210.