811865861 has 2 divisors, whose sum is σ = 811865862. Its totient is φ = 811865860.

The previous prime is 811865833. The next prime is 811865863. The reversal of 811865861 is 168568118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 811680100 + 185761 = 28490^2 + 431^2 .

It is a cyclic number.

It is not a de Polignac number, because 811865861 - 2¹⁸ = 811603717 is a prime.

Together with 811865863, 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 (811865863) 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, 405932930 + 405932931.

It is an arithmetic number, because the mean of its divisors is an integer number (405932931).

Almost surely, 2^811865861 is an apocalyptic number.

It is an amenable number.

811865861 is a deficient number, since it is larger than the sum of its proper divisors (1).

811865861 is an equidigital number, since it uses as much as digits as its factorization.

811865861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 92160, while the sum is 44.

The square root of 811865861 is about 28493.2599223044. The cubic root of 811865861 is about 932.8849638772.

The spelling of 811865861 in words is "eight hundred eleven million, eight hundred sixty-five thousand, eight hundred sixty-one".