81868664 has 16 divisors (see below), whose sum is σ = 154144320. Its totient is φ = 40763520.

The previous prime is 81868643. The next prime is 81868667. The reversal of 81868664 is 46686818.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81868667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19304 + ... + 23159.

It is an arithmetic number, because the mean of its divisors is an integer number (9634020).

Almost surely, 2^81868664 is an apocalyptic number.

It is an amenable number.

81868664 is a deficient number, since it is larger than the sum of its proper divisors (72275656).

81868664 is a wasteful number, since it uses less digits than its factorization.

81868664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42710 (or 42706 counting only the distinct ones).

The product of its digits is 442368, while the sum is 47.

The square root of 81868664 is about 9048.1304146216. The cubic root of 81868664 is about 434.2160787719.

The spelling of 81868664 in words is "eighty-one million, eight hundred sixty-eight thousand, six hundred sixty-four".