81608865 has 32 divisors (see below), whose sum is σ = 144431616. Its totient is φ = 39087360.

The previous prime is 81608861. The next prime is 81608867. The reversal of 81608865 is 56880618.

It is not a de Polignac number, because 81608865 - 2² = 81608861 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81608861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1560 + ... + 12870.

It is an arithmetic number, because the mean of its divisors is an integer number (4513488).

Almost surely, 2^81608865 is an apocalyptic number.

It is an amenable number.

81608865 is a deficient number, since it is larger than the sum of its proper divisors (62822751).

81608865 is a wasteful number, since it uses less digits than its factorization.

81608865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11369.

The product of its (nonzero) digits is 92160, while the sum is 42.

The square root of 81608865 is about 9033.7625051802. The cubic root of 81608865 is about 433.7562836308.

The spelling of 81608865 in words is "eighty-one million, six hundred eight thousand, eight hundred sixty-five".