81646664 has 16 divisors (see below), whose sum is σ = 167004720. Its totient is φ = 37112080.

The previous prime is 81646651. The next prime is 81646673. The reversal of 81646664 is 46664618.

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, 463814 + ... + 463989.

It is an arithmetic number, because the mean of its divisors is an integer number (10437795).

Almost surely, 2^81646664 is an apocalyptic number.

It is an amenable number.

81646664 is an abundant number, since it is smaller than the sum of its proper divisors (85358056).

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

81646664 is a wasteful number, since it uses less digits than its factorization.

81646664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 927820 (or 927816 counting only the distinct ones).

The product of its digits is 165888, while the sum is 41.

The square root of 81646664 is about 9035.8543591627. The cubic root of 81646664 is about 433.8232413202.

The spelling of 81646664 in words is "eighty-one million, six hundred forty-six thousand, six hundred sixty-four".