221 (number)

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← 220 221 222 →
Cardinal two hundred twenty-one
Ordinal 221st
(two hundred twenty-first)
Factorization 13 × 17
Greek numeral ΣΚΑ´
Roman numeral CCXXI, ccxxi
Binary 110111012
Ternary 220123
Senary 10056
Octal 3358
Duodecimal 16512
Hexadecimal DD16

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

In mathematics

Its factorization as 13 × 17 makes 221 the product of two consecutive prime numbers, the sixth smallest such product. [1]

221 is a centered square number. [2]

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References

  1. ↑ Sloane, N. J. A. (ed.). "SequenceA006094(Products of 2 successive primes)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
  2. ↑ Sloane, N. J. A. (ed.). "SequenceA001844(Centered square numbers)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
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