81981159137280 has 2688 divisors, whose sum is σ = 330628735906560. Its totient is φ = 18635795988480.

The previous prime is 81981159137249. The next prime is 81981159137347. The reversal of 81981159137280 is 8273195118918.

81981159137280 is a `hidden beast` number, since 8 + 1 + 9 + 8 + 1 + 1 + 591 + 37 + 2 + 8 + 0 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 598402621372 + ... + 598402621508.

It is an arithmetic number, because the mean of its divisors is an integer number (123001761870).

Almost surely, 2^{81981159137280} is an apocalyptic number.

81981159137280 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 81981159137280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (165314367953280).

81981159137280 is an abundant number, since it is smaller than the sum of its proper divisors (248647576769280).

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

81981159137280 is a wasteful number, since it uses less digits than its factorization.

81981159137280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360 (or 333 counting only the distinct ones).

The product of its (nonzero) digits is 8709120, while the sum is 63.

The spelling of 81981159137280 in words is "eighty-one trillion, nine hundred eighty-one billion, one hundred fifty-nine million, one hundred thirty-seven thousand, two hundred eighty".