81320864 has 24 divisors (see below), whose sum is σ = 160497540. Its totient is φ = 40559616.

The previous prime is 81320807. The next prime is 81320873. The reversal of 81320864 is 46802318.

It can be written as a sum of positive squares in 2 ways, for example, as 65480464 + 15840400 = 8092^2 + 3980^2 .

It is a super-2 number, since 2×81320864² = 13226165843412992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a self number, because there is not a number n which added to its sum of digits gives 81320864.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 10922 + ... + 16790.

Almost surely, 2^81320864 is an apocalyptic number.

It is an amenable number.

81320864 is a deficient number, since it is larger than the sum of its proper divisors (79176676).

81320864 is a wasteful number, since it uses less digits than its factorization.

81320864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6312 (or 6304 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 81320864 is about 9017.8081594143. The cubic root of 81320864 is about 433.2454343739.

The spelling of 81320864 in words is "eighty-one million, three hundred twenty thousand, eight hundred sixty-four".