81397069657920 has 336 divisors, whose sum is σ = 283475039807232. Its totient is φ = 21434539069440.

The previous prime is 81397069657853. The next prime is 81397069657933. The reversal of 81397069657920 is 2975696079318.

81397069657920 is a `hidden beast` number, since 81 + 397 + 0 + 6 + 96 + 5 + 79 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 528918585 + ... + 529072455.

It is an arithmetic number, because the mean of its divisors is an integer number (843675713712).

Almost surely, 2^{81397069657920} is an apocalyptic number.

81397069657920 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 81397069657920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141737519903616).

81397069657920 is an abundant number, since it is smaller than the sum of its proper divisors (202077970149312).

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

81397069657920 is a wasteful number, since it uses less digits than its factorization.

81397069657920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156190 (or 156177 counting only the distinct ones).

The product of its (nonzero) digits is 308629440, while the sum is 72.

The spelling of 81397069657920 in words is "eighty-one trillion, three hundred ninety-seven billion, sixty-nine million, six hundred fifty-seven thousand, nine hundred twenty".