81720407704 has 128 divisors (see below), whose sum is σ = 173859840000. Its totient is φ = 35749900800.

The previous prime is 81720407689. The next prime is 81720407723. The reversal of 81720407704 is 40770402718.

It is a super-3 number, since 3×81720407704³ (a number of 34 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 66384769 + ... + 66385999.

It is an arithmetic number, because the mean of its divisors is an integer number (1358280000).

Almost surely, 2^81720407704 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 81720407704, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (86929920000).

81720407704 is an abundant number, since it is smaller than the sum of its proper divisors (92139432296).

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

81720407704 is a wasteful number, since it uses less digits than its factorization.

81720407704 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1689 (or 1685 counting only the distinct ones).

The product of its (nonzero) digits is 87808, while the sum is 40.

The spelling of 81720407704 in words is "eighty-one billion, seven hundred twenty million, four hundred seven thousand, seven hundred four".