21 in Roman Numerals
21 = XXI
21 is written XXI in Roman numerals.
Step by step
- Split 21 into place values: 20 + 1.
- 20 = XX
- 1 = I
- Join them from largest to smallest: XXI.
To read XXI back, go from left to right and add each value, treating a smaller symbol before a larger one as a single subtracted pair: X (10) + X (10) + I (1) = 21.
Details
- Symbols used
- X = 10, I = 1
- Roman numeral
- XXI
- Breakdown
- XX + I
- Number of symbols
- 3
- Lowercase
- xxi
- Uses subtraction
- No
How it works
Roman numerals combine seven symbols — I (1), V (5), X (10), L (50), C (100), D (500) and M (1,000). Write each place value of the number separately, from thousands down to ones, and join the results. Six subtractive pairs replace four repeated symbols: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). No symbol appears more than three times in a row.
Nearby values
Related conversions
Frequently asked questions
What is 21 in Roman numerals?
XXI.
How do you write 21 in Roman numerals?
Break it into XX (20) + I (1) and write XXI.
What number is XXI?
XXI = 21.
What is the largest standard Roman numeral?
3,999, written MMMCMXCIX.