81591868800 has 576 divisors, whose sum is σ = 314904844800. Its totient is φ = 19996508160.

The previous prime is 81591868753. The next prime is 81591868801. The reversal of 81591868800 is 886819518.

It is a tau number, because it is divible by the number of its divisors (576).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591868801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 143394916 + ... + 143395484.

It is an arithmetic number, because the mean of its divisors is an integer number (546709800).

Almost surely, 2^81591868800 is an apocalyptic number.

81591868800 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 81591868800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (157452422400).

81591868800 is an abundant number, since it is smaller than the sum of its proper divisors (233312976000).

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

81591868800 is a wasteful number, since it uses less digits than its factorization.

81591868800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 995 (or 975 counting only the distinct ones).

The product of its (nonzero) digits is 1105920, while the sum is 54.

The spelling of 81591868800 in words is "eighty-one billion, five hundred ninety-one million, eight hundred sixty-eight thousand, eight hundred".