81365580 has 96 divisors (see below), whose sum is σ = 256132800. Its totient is φ = 21441024.

The previous prime is 81365579. The next prime is 81365611. The reversal of 81365580 is 8556318.

81365580 is a `hidden beast` number, since 8 + 13 + 65 + 580 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 47214 + ... + 48906.

It is an arithmetic number, because the mean of its divisors is an integer number (2668050).

Almost surely, 2^81365580 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 81365580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128066400).

81365580 is an abundant number, since it is smaller than the sum of its proper divisors (174767220).

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

81365580 is a wasteful number, since it uses less digits than its factorization.

81365580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1800 (or 1792 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 36.

The square root of 81365580 is about 9020.2871351194. The cubic root of 81365580 is about 433.3248295504.

The spelling of 81365580 in words is "eighty-one million, three hundred sixty-five thousand, five hundred eighty".