81051797520 has 480 divisors, whose sum is σ = 293908867200. Its totient is φ = 19954999296.

The previous prime is 81051797513. The next prime is 81051797537. The reversal of 81051797520 is 2579715018.

81051797520 is a `hidden beast` number, since 8 + 1 + 0 + 51 + 79 + 7 + 520 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

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 95 ways as a sum of consecutive naturals, for example, 110575074 + ... + 110575806.

It is an arithmetic number, because the mean of its divisors is an integer number (612310140).

Almost surely, 2^81051797520 is an apocalyptic number.

81051797520 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81051797520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146954433600).

81051797520 is an abundant number, since it is smaller than the sum of its proper divisors (212857069680).

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

81051797520 is a wasteful number, since it uses less digits than its factorization.

81051797520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 967 (or 958 counting only the distinct ones).

The product of its (nonzero) digits is 176400, while the sum is 45.

The spelling of 81051797520 in words is "eighty-one billion, fifty-one million, seven hundred ninety-seven thousand, five hundred twenty".