81188865 has 32 divisors (see below), whose sum is σ = 146716800. Its totient is φ = 42586560.

The previous prime is 81188839. The next prime is 81188867. The reversal of 81188865 is 56888118.

It is a happy number.

It is not a de Polignac number, because 81188865 - 2⁸ = 81188609 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81188865.

It is not an unprimeable number, because it can be changed into a prime (81188867) 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, 3306 + ... + 13164.

It is an arithmetic number, because the mean of its divisors is an integer number (4584900).

Almost surely, 2^81188865 is an apocalyptic number.

It is an amenable number.

81188865 is a deficient number, since it is larger than the sum of its proper divisors (65527935).

81188865 is a wasteful number, since it uses less digits than its factorization.

81188865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9934 (or 9928 counting only the distinct ones).

The product of its digits is 122880, while the sum is 45.

The square root of 81188865 is about 9010.4863908670. The cubic root of 81188865 is about 433.0108945873.

It can be divided in two parts, 811 and 88865, that added together give a triangular number (89676 = T₄₂₃).

The spelling of 81188865 in words is "eighty-one million, one hundred eighty-eight thousand, eight hundred sixty-five".