281 (number)

281 is the natural number following 280 and preceding 282. It is also a prime number.

In mathematics

281 is a twin prime with 283, Sophie Germain prime, sum of the first fourteen primes, sum of seven consecutive primes, Chen prime, Eisenstein prime with no imaginary part, and a centered decagonal number.
281 is the smallest prime p such that the decimal period length of the reciprocal of p is /10, i.e. the period length of 1/281 is 28. However, in binary, it has period length 70.
The generalized repunit number is composite for all prime p < 60000.