191_(number)

191 (number)

191 (number)

Natural number

191 (one hundred [and] ninety-one) is the natural number following 190 and preceding 192.

Quick Facts ← 190 191 192 →, Cardinal ...

In mathematics

191 is a prime number, part of a prime quadruplet of four primes: 191, 193, 197, and 199.[1] Because doubling and adding one produces another prime number (383), 191 is a Sophie Germain prime.[2] It is the smallest prime that is not a full reptend prime in any base from 2 to 10; in fact, the smallest base for which 191 is a full period prime is base 19.[3]

See also

References

  1. [1]
    Sloane, N. J. A. (ed.). "Sequence A136162 (List of prime quadruplets {p, p+2, p+6, p+8})". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  2. [2]
    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.
  3. [3]
    Wolfram MathWorld; Primitive Root
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