81915816 has 32 divisors (see below), whose sum is σ = 205660800. Its totient is φ = 27189120.

The previous prime is 81915787. The next prime is 81915833. The reversal of 81915816 is 61851918.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1405 + ... + 12876.

It is an arithmetic number, because the mean of its divisors is an integer number (6426900).

Almost surely, 2^81915816 is an apocalyptic number.

It is an amenable number.

81915816 is an abundant number, since it is smaller than the sum of its proper divisors (123744984).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81915816 is a wasteful number, since it uses less digits than its factorization.

81915816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14529 (or 14525 counting only the distinct ones).

The product of its digits is 17280, while the sum is 39.

The square root of 81915816 is about 9050.7356607074. The cubic root of 81915816 is about 434.2994245688.

The spelling of 81915816 in words is "eighty-one million, nine hundred fifteen thousand, eight hundred sixteen".