← 190 191 192 →
Cardinalone hundred ninety-one
Ordinal191st
(one hundred ninety-first)
Factorizationprime
Primeyes
Greek numeralΡϞΑ´
Roman numeralCXCI
Binary101111112
Ternary210023
Octal2778
Duodecimal13B12
HexadecimalBF16

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

In mathematics

191 is a prime number, part of a prime quadruplet of four primes: 191, 193, 197, and 199. Because doubling and adding one produces another prime number (383), 191 is a Sophie Germain prime. 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.[1]

See also

References

  1. ^ Wolfram MathWorld; Primitive Root