81656664 has 32 divisors (see below), whose sum is σ = 204804720. Its totient is φ = 27130496.

The previous prime is 81656657. The next prime is 81656671. The reversal of 81656664 is 46665618.

It is an interprime number because it is at equal distance from previous prime (81656657) and next prime (81656671).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2242 + ... + 12974.

Almost surely, 2^81656664 is an apocalyptic number.

It is an amenable number.

81656664 is an abundant number, since it is smaller than the sum of its proper divisors (123148056).

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

81656664 is a wasteful number, since it uses less digits than its factorization.

81656664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11059 (or 11055 counting only the distinct ones).

The product of its digits is 207360, while the sum is 42.

The square root of 81656664 is about 9036.4076933259. The cubic root of 81656664 is about 433.8409520063.

The spelling of 81656664 in words is "eighty-one million, six hundred fifty-six thousand, six hundred sixty-four".