# 281 (number)

From HandWiki

__: Natural number__

**Short description**
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Cardinal | two hundred eighty-one | |||

Ordinal | 281st (two hundred eighty-first) | |||

Factorization | prime | |||

Prime | 60th | |||

Greek numeral | ΣΠΑ´ | |||

Roman numeral | CCLXXXI | |||

Binary | 100011001_{2} | |||

Ternary | 101102_{3} | |||

Quaternary | 10121_{4} | |||

Quinary | 2111_{5} | |||

Senary | 1145_{6} | |||

Octal | 431_{8} | |||

Duodecimal | 1B5_{12} | |||

Hexadecimal | 119_{16} | |||

Vigesimal | E1_{20} | |||

Base 36 | 7T_{36} |

281 is the 60th prime, twin prime with 283, Sophie Germain prime, sum of the first fourteen primes, sum of seven consecutive primes (29 + 31 + 37 + 41 + 43 + 47 + 53), Chen prime, Eisenstein prime with no imaginary part, centered decagonal number.

281 is the smallest prime *p* such that the decimal period length of the reciprocal of *p* is (*p*−1)/10, i.e. the period length of 1/281 is 28. However, in binary, it has period length 70.

The generalized repunit number [math]\displaystyle{ \frac{281^p-1}{280} }[/math] is composite for all prime *p* < 60000.

NANP telephone area code 281 is an overlay code serving Houston, Texas, and its environs.

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Original source: https://en.wikipedia.org/wiki/281 (number).
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