81181688064 has 72 divisors (see below), whose sum is σ = 216109192992. Its totient is φ = 27054612480.

The previous prime is 81181688057. The next prime is 81181688083. The reversal of 81181688064 is 46088618118.

It is a junction number, because it is equal to n+sod(n) for n = 81181687998 and 81181688016.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4755384 + ... + 4772424.

Almost surely, 2^81181688064 is an apocalyptic number.

It is an amenable number.

81181688064 is an abundant number, since it is smaller than the sum of its proper divisors (134927504928).

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

81181688064 is a wasteful number, since it uses less digits than its factorization.

81181688064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23263 (or 23249 counting only the distinct ones).

The product of its (nonzero) digits is 589824, while the sum is 51.

The spelling of 81181688064 in words is "eighty-one billion, one hundred eighty-one million, six hundred eighty-eight thousand, sixty-four".