81518664 has 64 divisors (see below), whose sum is σ = 218635200. Its totient is φ = 25249536.

The previous prime is 81518653. The next prime is 81518687. The reversal of 81518664 is 46681518.

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22482 + ... + 25854.

It is an arithmetic number, because the mean of its divisors is an integer number (3416175).

Almost surely, 2^81518664 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 81518664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109317600).

81518664 is an abundant number, since it is smaller than the sum of its proper divisors (137116536).

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

81518664 is a wasteful number, since it uses less digits than its factorization.

81518664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3454 (or 3450 counting only the distinct ones).

The product of its digits is 46080, while the sum is 39.

The square root of 81518664 is about 9028.7686868144. The cubic root of 81518664 is about 433.5964167085.

The spelling of 81518664 in words is "eighty-one million, five hundred eighteen thousand, six hundred sixty-four".