81756564 has 24 divisors (see below), whose sum is σ = 191005248. Its totient is φ = 27217920.

The previous prime is 81756541. The next prime is 81756593. The reversal of 81756564 is 46565718.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 6804 + ... + 14484.

It is an arithmetic number, because the mean of its divisors is an integer number (7958552).

Almost surely, 2^81756564 is an apocalyptic number.

It is an amenable number.

81756564 is an abundant number, since it is smaller than the sum of its proper divisors (109248684).

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

81756564 is a wasteful number, since it uses less digits than its factorization.

81756564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8575 (or 8573 counting only the distinct ones).

The product of its digits is 201600, while the sum is 42.

The square root of 81756564 is about 9041.9336427558. The cubic root of 81756564 is about 434.0178024368.

The spelling of 81756564 in words is "eighty-one million, seven hundred fifty-six thousand, five hundred sixty-four".