815978831 has 4 divisors (see below), whose sum is σ = 831374712. Its totient is φ = 800582952.

The previous prime is 815978827. The next prime is 815978833. The reversal of 815978831 is 138879518.

815978831 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 138879518 = 2 ⋅69439759.

It is a cyclic number.

It is not a de Polignac number, because 815978831 - 2² = 815978827 is a prime.

It is a super-2 number, since 2×815978831² = 1331642905280253122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 815978831.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (815978833) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7697861 + ... + 7697966.

It is an arithmetic number, because the mean of its divisors is an integer number (207843678).

Almost surely, 2^815978831 is an apocalyptic number.

815978831 is a deficient number, since it is larger than the sum of its proper divisors (15395881).

815978831 is a wasteful number, since it uses less digits than its factorization.

815978831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15395880.

The product of its digits is 483840, while the sum is 50.

The square root of 815978831 is about 28565.3431801545. The cubic root of 815978831 is about 934.4576648392.

The spelling of 815978831 in words is "eight hundred fifteen million, nine hundred seventy-eight thousand, eight hundred thirty-one".