391691 has 2 divisors, whose sum is σ = 391692. Its totient is φ = 391690.

The previous prime is 391679. The next prime is 391693. The reversal of 391691 is 196193.

It is a strong prime.

It is an emirp because it is prime and its reverse (196193) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 391691 - 2⁶ = 391627 is a prime.

Together with 391693, it forms a pair of twin primes.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 391691.

It is not a weakly prime, because it can be changed into another prime (391693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195845 + 195846.

It is an arithmetic number, because the mean of its divisors is an integer number (195846).

2³⁹¹⁶⁹¹ is an apocalyptic number.

391691 is a deficient number, since it is larger than the sum of its proper divisors (1).

391691 is an equidigital number, since it uses as much as digits as its factorization.

391691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1458, while the sum is 29.

The square root of 391691 is about 625.8522189783. The cubic root of 391691 is about 73.1668791206.

The spelling of 391691 in words is "three hundred ninety-one thousand, six hundred ninety-one".