191 has 2 divisors, whose sum is σ = 192. Its totient is φ = 190.

The previous prime is 181. The next prime is 193.

Adding to 191 its sum of digits (11), we get a palindrome (202).

191 is nontrivially palindromic in base 6, base 9 and base 10.

191 is an esthetic number in base 9 and base 15, because in such bases its adjacent digits differ by 1.

It is a strong prime.

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 191 - 2^{6} = 127 is a prime.

It is a Sophie Germain prime.

Together with 193, it forms a pair of twin primes.

It is a Chen prime.

It is a pancake number, because a pancake can be divided into 191 parts by 19 straight cuts.

191 is an undulating number in base 6, base 9 and base 10.

It is a plaindrome in base 4, base 8, base 12, base 13 and base 16.

It is a nialpdrome in base 14 and base 15.

It is a congruent number.

Being equal to 3×4^{3}-1, it is a generalized Woodall number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95 + 96.

It is an arithmetic number, because the mean of its divisors is an integer number (96).

191 is a deficient number, since it is larger than the sum of its proper divisors (1).

191 is an equidigital number, since it uses as much as digits as its factorization.

191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9, while the sum is 11.

The square root of 191 is about 13.8202749611. The cubic root of 191 is about 5.7589652205.

The spelling of 191 in words is "one hundred ninety-one", and thus it is an aban number.

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