How Can We Help?
You are here:
< Back
Natural 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,[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, 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 (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 is composite for all prime p < 60000.
References
- ^ Sloane, N. J. A. (ed.). "Sequence A001359 (Lesser of twin primes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
- ^ Sloane, N. J. A. (ed.). "Sequence A005384 (Sophie Germain primes p: 2p+1 is also prime)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
|
Categories
-
Annuals36
-
Bulbs, Corms & Tubers41
-
Ferns27
-
Fruits3
-
Garden Plants23
-
Grasses26
-
Herb17
-
Insects1
-
Mammals1
-
Midwest Native Plants0
-
Northeast Native Plants112
-
Perennials123
-
Rose1
-
Shrubs47
-
Trees112
-
Tropical Plants53
-
Upland Birds5
-
Vines18
-
Viola Tricolor1
-
Water Gardening & Plants9
-
Waterfowl0
-
Wetland Birds0
-
Wetland Plants4
-
Wildbirds172
-
Wildflowers1
-
Woodland Plants29
Table of Contents
Recent Comments