391891 has 2 divisors, whose sum is σ = 391892. Its totient is φ = 391890.

The previous prime is 391889. The next prime is 391903. The reversal of 391891 is 198193.

It is a weak prime.

It is an emirp because it is prime and its reverse (198193) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 391891 - 2¹ = 391889 is a prime.

Together with 391889, it forms a pair of twin primes.

It is a Chen prime.

391891 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (391801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195945 + 195946.

It is an arithmetic number, because the mean of its divisors is an integer number (195946).

2³⁹¹⁸⁹¹ is an apocalyptic number.

391891 is a deficient number, since it is larger than the sum of its proper divisors (1).

391891 is an equidigital number, since it uses as much as digits as its factorization.

391891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1944, while the sum is 31.

The square root of 391891 is about 626.0119807160. The cubic root of 391891 is about 73.1793301648.

The spelling of 391891 in words is "three hundred ninety-one thousand, eight hundred ninety-one".