815957861 has 2 divisors, whose sum is σ = 815957862. Its totient is φ = 815957860.

The previous prime is 815957839. The next prime is 815957881. The reversal of 815957861 is 168759518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 796650625 + 19307236 = 28225^2 + 4394^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-815957861 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (815957881) 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, 407978930 + 407978931.

It is an arithmetic number, because the mean of its divisors is an integer number (407978931).

Almost surely, 2^815957861 is an apocalyptic number.

It is an amenable number.

815957861 is a deficient number, since it is larger than the sum of its proper divisors (1).

815957861 is an equidigital number, since it uses as much as digits as its factorization.

815957861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 604800, while the sum is 50.

The square root of 815957861 is about 28564.9761246181. The cubic root of 815957861 is about 934.4496598337.

The spelling of 815957861 in words is "eight hundred fifteen million, nine hundred fifty-seven thousand, eight hundred sixty-one".