81131887584 has 576 divisors, whose sum is σ = 273762478080. Its totient is φ = 22546944000.

The previous prime is 81131887567. The next prime is 81131887657. The reversal of 81131887584 is 48578813118.

It is a self number, because there is not a number n which added to its sum of digits gives 81131887584.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 173729719 + ... + 173730185.

It is an arithmetic number, because the mean of its divisors is an integer number (475282080).

Almost surely, 2^81131887584 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 81131887584, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (136881239040).

81131887584 is an abundant number, since it is smaller than the sum of its proper divisors (192630590496).

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

81131887584 is a wasteful number, since it uses less digits than its factorization.

81131887584 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 615 (or 604 counting only the distinct ones).

The product of its digits is 1720320, while the sum is 54.

The spelling of 81131887584 in words is "eighty-one billion, one hundred thirty-one million, eight hundred eighty-seven thousand, five hundred eighty-four".