21 (number)
Natural number / From Wikipedia, the free encyclopedia
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"XXI" and "Twenty-One" redirect here. For other uses, see 21.
21 (twenty-one) is the natural number following 20 and preceding 22.
Quick Facts ← 20 21 22 →, Cardinal ...
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Cardinal | twenty-one | |||
Ordinal | 21st (twenty-first) | |||
Factorization | 3 × 7 | |||
Divisors | 1, 3, 7, 21 | |||
Greek numeral | ΚΑ´ | |||
Roman numeral | XXI | |||
Binary | 101012 | |||
Ternary | 2103 | |||
Senary | 336 | |||
Octal | 258 | |||
Duodecimal | 1912 | |||
Hexadecimal | 1516 |
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The current century is the 21st century AD, under the Gregorian calendar.