81737821440 has 576 divisors, whose sum is σ = 318236083200. Its totient is φ = 19701964800.

The previous prime is 81737821409. The next prime is 81737821481. The reversal of 81737821440 is 4412873718.

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

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 80213251 + ... + 80214269.

It is an arithmetic number, because the mean of its divisors is an integer number (552493200).

Almost surely, 2^81737821440 is an apocalyptic number.

81737821440 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 81737821440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (159118041600).

81737821440 is an abundant number, since it is smaller than the sum of its proper divisors (236498261760).

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

81737821440 is a wasteful number, since it uses less digits than its factorization.

81737821440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1271 (or 1251 counting only the distinct ones).

The product of its (nonzero) digits is 301056, while the sum is 45.

The spelling of 81737821440 in words is "eighty-one billion, seven hundred thirty-seven million, eight hundred twenty-one thousand, four hundred forty".