221 (number)

220 221 222
Cardinal two hundred twenty-one
Ordinal 221st
(two hundred and twenty-first)
Factorization 13 × 17
Roman numeral CCXXI
Binary 110111012
Ternary 220123
Quaternary 31314
Quinary 13415
Senary 10056
Octal 3358
Duodecimal 16512
Hexadecimal DD16
Vigesimal B120
Base 36 6536

221 (two hundred [and] twenty-one) is the natural number following 220 and preceding 222.

In mathematics

221 is:

In other fields

221 is:

Historical years

221 A.D. and 221 B.C.


  1. "Sloane's A001844 : Centered square numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.
  2. Conan Doyle, Sir Arthur A Study in Scarlet pub. Wordsworth Editions Limited (2004) p.10 "We met next day, as [Holmes] had arranged, and inspected the rooms at No. 221B Baker Street, of which he had spoken at our meeting." ISBN 978-1-84022-411-5
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