191691287 has 2 divisors, whose sum is σ = 191691288. Its totient is φ = 191691286.

The previous prime is 191691271. The next prime is 191691289. The reversal of 191691287 is 782196191.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 191691287 - 2⁴ = 191691271 is a prime.

Together with 191691289, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191691289) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95845643 + 95845644.

It is an arithmetic number, because the mean of its divisors is an integer number (95845644).

Almost surely, 2^191691287 is an apocalyptic number.

191691287 is a deficient number, since it is larger than the sum of its proper divisors (1).

191691287 is an equidigital number, since it uses as much as digits as its factorization.

191691287 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 44.

The square root of 191691287 is about 13845.2622582600. The cubic root of 191691287 is about 576.5904669865.

The spelling of 191691287 in words is "one hundred ninety-one million, six hundred ninety-one thousand, two hundred eighty-seven".