81591534964 has 6 divisors (see below), whose sum is σ = 142785186194. Its totient is φ = 40795767480.

The previous prime is 81591534961. The next prime is 81591535001. The reversal of 81591534964 is 46943519518.

It can be written as a sum of positive squares in only one way, i.e., 81543371364 + 48163600 = 285558^2 + 6940^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591534961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10198941867 + ... + 10198941874.

Almost surely, 2^81591534964 is an apocalyptic number.

It is an amenable number.

81591534964 is a deficient number, since it is larger than the sum of its proper divisors (61193651230).

81591534964 is a wasteful number, since it uses less digits than its factorization.

81591534964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20397883745 (or 20397883743 counting only the distinct ones).

The product of its digits is 4665600, while the sum is 55.

The spelling of 81591534964 in words is "eighty-one billion, five hundred ninety-one million, five hundred thirty-four thousand, nine hundred sixty-four".