81197664 has 24 divisors (see below), whose sum is σ = 213144120. Its totient is φ = 27065856.

The previous prime is 81197663. The next prime is 81197689. The reversal of 81197664 is 46679118.

It is a tau number, because it is divible by the number of its divisors (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81197663) 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, 422809 + ... + 423000.

It is an arithmetic number, because the mean of its divisors is an integer number (8881005).

Almost surely, 2^81197664 is an apocalyptic number.

It is an amenable number.

81197664 is an abundant number, since it is smaller than the sum of its proper divisors (131946456).

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

81197664 is a wasteful number, since it uses less digits than its factorization.

81197664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 845822 (or 845814 counting only the distinct ones).

The product of its digits is 72576, while the sum is 42.

The square root of 81197664 is about 9010.9746420684. The cubic root of 81197664 is about 433.0265368194.

The spelling of 81197664 in words is "eighty-one million, one hundred ninety-seven thousand, six hundred sixty-four".