815291991 has 12 divisors (see below), whose sum is σ = 1177944768. Its totient is φ = 543389184.

The previous prime is 815291963. The next prime is 815292019. The reversal of 815291991 is 199192518.

815291991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (815291963) and next prime (815292019).

It is not a de Polignac number, because 815291991 - 2⁶ = 815291927 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (815291891) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35866 + ... + 54008.

It is an arithmetic number, because the mean of its divisors is an integer number (98162064).

Almost surely, 2^815291991 is an apocalyptic number.

815291991 is a deficient number, since it is larger than the sum of its proper divisors (362652777).

815291991 is a wasteful number, since it uses less digits than its factorization.

815291991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23142 (or 23139 counting only the distinct ones).

The product of its digits is 58320, while the sum is 45.

The square root of 815291991 is about 28553.3183885866. The cubic root of 815291991 is about 934.1954018798.

The spelling of 815291991 in words is "eight hundred fifteen million, two hundred ninety-one thousand, nine hundred ninety-one".