81563904 has 54 divisors (see below), whose sum is σ = 235175486. Its totient is φ = 27187200.

The previous prime is 81563899. The next prime is 81563929. The reversal of 81563904 is 40936518.

81563904 is a `hidden beast` number, since 8 + 1 + 563 + 90 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 58982400 + 22581504 = 7680^2 + 4752^2 .

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 5 ways as a sum of consecutive naturals, for example, 15397 + ... + 20004.

Almost surely, 2^81563904 is an apocalyptic number.

It is an amenable number.

81563904 is an abundant number, since it is smaller than the sum of its proper divisors (153611582).

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

81563904 is a wasteful number, since it uses less digits than its factorization.

81563904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35423 (or 35406 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 81563904 is about 9031.2736643289. The cubic root of 81563904 is about 433.6766121441.

The spelling of 81563904 in words is "eighty-one million, five hundred sixty-three thousand, nine hundred four".