81520921152 has 448 divisors, whose sum is σ = 268145971200. Its totient is φ = 24077813760.

The previous prime is 81520921147. The next prime is 81520921177. The reversal of 81520921152 is 25112902518.

81520921152 is a `hidden beast` number, since 81 + 520 + 9 + 2 + 1 + 1 + 52 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 176070873 + ... + 176071335.

Almost surely, 2^81520921152 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 81520921152, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134072985600).

81520921152 is an abundant number, since it is smaller than the sum of its proper divisors (186625050048).

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

81520921152 is a wasteful number, since it uses less digits than its factorization.

81520921152 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 711 (or 695 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 36.

The spelling of 81520921152 in words is "eighty-one billion, five hundred twenty million, nine hundred twenty-one thousand, one hundred fifty-two".