81611511072 has 384 divisors, whose sum is σ = 278559590400. Its totient is φ = 20316635136.

The previous prime is 81611511049. The next prime is 81611511083. The reversal of 81611511072 is 27011511618.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 55935879 + ... + 55937337.

It is an arithmetic number, because the mean of its divisors is an integer number (725415600).

Almost surely, 2^81611511072 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 81611511072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139279795200).

81611511072 is an abundant number, since it is smaller than the sum of its proper divisors (196948079328).

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

81611511072 is a wasteful number, since it uses less digits than its factorization.

81611511072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1848 (or 1840 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 33.

The spelling of 81611511072 in words is "eighty-one billion, six hundred eleven million, five hundred eleven thousand, seventy-two".