81556992 has 120 divisors (see below), whose sum is σ = 256936680. Its totient is φ = 24698880.

The previous prime is 81556967. The next prime is 81557009. The reversal of 81556992 is 29965518.

81556992 is a `hidden beast` number, since 8 + 1 + 556 + 9 + 92 = 666.

It is a congruent number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 49884 + ... + 51492.

It is an arithmetic number, because the mean of its divisors is an integer number (2141139).

Almost surely, 2^81556992 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81556992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128468340).

81556992 is an abundant number, since it is smaller than the sum of its proper divisors (175379688).

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

81556992 is a wasteful number, since it uses less digits than its factorization.

81556992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1644 (or 1625 counting only the distinct ones).

The product of its digits is 194400, while the sum is 45.

The square root of 81556992 is about 9030.8909859437. The cubic root of 81556992 is about 433.6643613923.

The spelling of 81556992 in words is "eighty-one million, five hundred fifty-six thousand, nine hundred ninety-two".