81656964 has 48 divisors (see below), whose sum is σ = 213608640. Its totient is φ = 26974080.

The previous prime is 81656963. The next prime is 81656989. The reversal of 81656964 is 46965618.

81656964 is a `hidden beast` number, since 81 + 6 + 569 + 6 + 4 = 666.

It is not an unprimeable number, because it can be changed into a prime (81656963) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8859 + ... + 15549.

It is an arithmetic number, because the mean of its divisors is an integer number (4450180).

Almost surely, 2^81656964 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81656964, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (106804320).

81656964 is an abundant number, since it is smaller than the sum of its proper divisors (131951676).

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

81656964 is a wasteful number, since it uses less digits than its factorization.

81656964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6817 (or 6809 counting only the distinct ones).

The product of its digits is 311040, while the sum is 45.

The square root of 81656964 is about 9036.4242928273. The cubic root of 81656964 is about 433.8414833045.

It can be divided in two parts, 8165 and 6964, that added together give a square (15129 = 123²).

The spelling of 81656964 in words is "eighty-one million, six hundred fifty-six thousand, nine hundred sixty-four".