81597611811840 has 352 divisors, whose sum is σ = 262655482800000. Its totient is φ = 21620463501312.

The previous prime is 81597611811811. The next prime is 81597611811841. The reversal of 81597611811840 is 4811811679518.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (60).

It is not an unprimeable number, because it can be changed into a prime (81597611811841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1755179316 + ... + 1755225804.

Almost surely, 2^{81597611811840} is an apocalyptic number.

81597611811840 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 81597611811840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (131327741400000).

81597611811840 is an abundant number, since it is smaller than the sum of its proper divisors (181057870988160).

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

81597611811840 is a wasteful number, since it uses less digits than its factorization.

81597611811840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47245 (or 47227 counting only the distinct ones).

The product of its (nonzero) digits is 3870720, while the sum is 60.

The spelling of 81597611811840 in words is "eighty-one trillion, five hundred ninety-seven billion, six hundred eleven million, eight hundred eleven thousand, eight hundred forty".