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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,cclxxxi | |||
| Binary | 1000110012 | |||
| Ternary | 1011023 | |||
| Senary | 11456 | |||
| Octal | 4318 | |||
| Duodecimal | 1B512 | |||
| Hexadecimal | 11916 | |||
281 is thenatural number following280 and preceding282. It is also aprime number.
281 is atwin prime with 283,[1]Sophie Germain prime,[2] sum of the first fourteen primes, sum of seven consecutive primes (29 + 31 + 37 + 41 + 43 + 47 + 53),Chen prime,[3]Eisenstein prime with no imaginary part, and acentered decagonal number.[4]
281 is the smallest primep such that thedecimalperiod length of thereciprocal ofp is (p−1)/10, i.e. the period length of 1/281 is 28. However, inbinary, it has period length 70.
The generalizedrepunit number iscomposite for all primep < 60000.
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