811931 has 2 divisors, whose sum is σ = 811932. Its totient is φ = 811930.

The previous prime is 811919. The next prime is 811933. The reversal of 811931 is 139118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 811931 - 2¹⁰ = 810907 is a prime.

It is a super-2 number, since 2×811931² = 1318463897522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 811933, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 811897 and 811906.

It is not a weakly prime, because it can be changed into another prime (811933) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 405965 + 405966.

It is an arithmetic number, because the mean of its divisors is an integer number (405966).

2⁸¹¹⁹³¹ is an apocalyptic number.

811931 is a deficient number, since it is larger than the sum of its proper divisors (1).

811931 is an equidigital number, since it uses as much as digits as its factorization.

811931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216, while the sum is 23.

The square root of 811931 is about 901.0721391764. The cubic root of 811931 is about 93.2909912813.

The spelling of 811931 in words is "eight hundred eleven thousand, nine hundred thirty-one".