81563784 has 16 divisors (see below), whose sum is σ = 203909520. Its totient is φ = 27187920.

The previous prime is 81563761. The next prime is 81563809. The reversal of 81563784 is 48736518.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1699222 + ... + 1699269.

It is an arithmetic number, because the mean of its divisors is an integer number (12744345).

Almost surely, 2^81563784 is an apocalyptic number.

It is an amenable number.

81563784 is an abundant number, since it is smaller than the sum of its proper divisors (122345736).

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

81563784 is a wasteful number, since it uses less digits than its factorization.

81563784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3398500 (or 3398496 counting only the distinct ones).

The product of its digits is 161280, while the sum is 42.

The square root of 81563784 is about 9031.2670207452. The cubic root of 81563784 is about 433.6763994633.

The spelling of 81563784 in words is "eighty-one million, five hundred sixty-three thousand, seven hundred eighty-four".