81505868 has 24 divisors (see below), whose sum is σ = 147058800. Its totient is φ = 39502080.

The previous prime is 81505867. The next prime is 81505901. The reversal of 81505868 is 86850518.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is not an unprimeable number, because it can be changed into a prime (81505867) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25208 + ... + 28256.

It is an arithmetic number, because the mean of its divisors is an integer number (6127450).

Almost surely, 2^81505868 is an apocalyptic number.

It is an amenable number.

81505868 is a deficient number, since it is larger than the sum of its proper divisors (65552932).

81505868 is a wasteful number, since it uses less digits than its factorization.

81505868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3257 (or 3255 counting only the distinct ones).

The product of its (nonzero) digits is 76800, while the sum is 41.

The square root of 81505868 is about 9028.0600352457. The cubic root of 81505868 is about 433.5737282844.

The spelling of 81505868 in words is "eighty-one million, five hundred five thousand, eight hundred sixty-eight".