21 in Roman Numerals

21 in Roman numerals is XXI.

XXI
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Decomposition

20 + 1

XX + I

XXI

Symbol breakdown

Symbol breakdown for XXI
TokenValueNotation
X 10 Additive — X = 10
X 10 Additive — X = 10
I 1 Additive — I = 1

Therefore: 20 + 1 = 21

Place values

Place-value breakdown for 21
PlaceValueRoman
Tens 20 XX
Ones 1 I

Final: XXI

Roman numeral length

XXI uses 3 characters.

Symbol frequency

SymbolCount
X× 2
I× 1

Subtractive pairs

XXI is written entirely with additive combinations—no IV, IX, XL, XC, CD, or CM pairs appear.

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← 20 in Roman numerals (XX) 22 in Roman numerals (XXII) →

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Neighboring values

Numbers near 21
NumberRoman numeral
17 XVII
18 XVIII
19 XIX
20 XX
21 XXI
22 XXII
23 XXIII
24 XXIV
25 XXV

Related round numbers

4 · IV 9 · IX 10 · X 20 · XX 30 · XXX 40 · XL 49 · XLIX 90 · XC 99 · XCIX 100 · C 400 · CD 500 · D

Related chart: Roman numerals 1–50 · Interactive chart tool

Common questions about 21

What is 21 in Roman numerals?

21 in Roman numerals is XXI.

How do you write 21 in Roman numerals?

Write 21 as XXI using additive combinations of the standard symbols.

Is XXI the correct Roman numeral for 21?

Yes. XXI is the canonical standard Roman numeral for 21 in the 1–3999 range.

What number is XXI?

XXI equals 21.

Link to this reference

Teachers and writers are welcome to link to this page.

https://roman-numerals.net/numbers/21-in-roman-numerals/