81664512 has 80 divisors (see below), whose sum is σ = 220640640. Its totient is φ = 26836992.

The previous prime is 81664511. The next prime is 81664519. The reversal of 81664512 is 21546618.

It is not an unprimeable number, because it can be changed into a prime (81664511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121008 + ... + 121680.

It is an arithmetic number, because the mean of its divisors is an integer number (2758008).

Almost surely, 2^81664512 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 81664512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (110320320).

81664512 is an abundant number, since it is smaller than the sum of its proper divisors (138976128).

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

81664512 is an equidigital number, since it uses as much as digits as its factorization.

81664512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 773 (or 757 counting only the distinct ones).

The product of its digits is 11520, while the sum is 33.

The square root of 81664512 is about 9036.8419262484. The cubic root of 81664512 is about 433.8548503401.

The spelling of 81664512 in words is "eighty-one million, six hundred sixty-four thousand, five hundred twelve".