81928505856 has 320 divisors, whose sum is σ = 235109952000. Its totient is φ = 25277054976.

The previous prime is 81928505851. The next prime is 81928505863. The reversal of 81928505856 is 65850582918.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is a junction number, because it is equal to n+sod(n) for n = 81928505796 and 81928505805.

It is not an unprimeable number, because it can be changed into a prime (81928505851) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 360918415 + ... + 360918641.

It is an arithmetic number, because the mean of its divisors is an integer number (734718600).

Almost surely, 2^81928505856 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 81928505856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117554976000).

81928505856 is an abundant number, since it is smaller than the sum of its proper divisors (153181446144).

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

81928505856 is a wasteful number, since it uses less digits than its factorization.

81928505856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499 (or 483 counting only the distinct ones).

The product of its (nonzero) digits is 6912000, while the sum is 57.

The spelling of 81928505856 in words is "eighty-one billion, nine hundred twenty-eight million, five hundred five thousand, eight hundred fifty-six".