21 in words
British English
twenty-one
The first hyphenated number. Every compound from twenty-one to ninety-nine takes one.
Quick reference
- In figures
- 21
- British English
- twenty-one
- American English
- The same (why they differ)
- Ordinal
- twenty-first (21st)
- Roman numeral
- XXI
- Place value
- 2 in the tens column; 1 in the ones column
- Expanded form
- 20 + 1
- Standard form
- 2.1 × 10¹
- Even or odd
- Odd
- Prime factors
- 3 × 7
Convert any other number, up to thirty-six digits.