81211564 has 12 divisors (see below), whose sum is σ = 162423184. Its totient is φ = 34804944.

The previous prime is 81211523. The next prime is 81211573. The reversal of 81211564 is 46511218.

81211564 is an admirable number.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (28), and also a Moran number because the ratio is a prime number: 2900413 = 81211564 / (8 + 1 + 2 + 1 + 1 + 5 + 6 + 4).

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 3 ways as a sum of consecutive naturals, for example, 1450179 + ... + 1450234.

Almost surely, 2^81211564 is an apocalyptic number.

It is an amenable number.

81211564 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

81211564 is a wasteful number, since it uses less digits than its factorization.

81211564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2900424 (or 2900422 counting only the distinct ones).

The product of its digits is 1920, while the sum is 28.

The square root of 81211564 is about 9011.7458907805. The cubic root of 81211564 is about 433.0512449417.

The spelling of 81211564 in words is "eighty-one million, two hundred eleven thousand, five hundred sixty-four".