81729089688 has 128 divisors (see below), whose sum is σ = 222306508800. Its totient is φ = 24974476800.

The previous prime is 81729089623. The next prime is 81729089707. The reversal of 81729089688 is 88698092718.

It is a Cunningham number, because it is equal to 285883²-1.

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, 1107793 + ... + 1179263.

It is an arithmetic number, because the mean of its divisors is an integer number (1736769600).

Almost surely, 2^81729089688 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 81729089688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (111153254400).

81729089688 is an abundant number, since it is smaller than the sum of its proper divisors (140577419112).

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

81729089688 is a wasteful number, since it uses less digits than its factorization.

81729089688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71593 (or 71589 counting only the distinct ones).

The product of its (nonzero) digits is 27869184, while the sum is 66.

The spelling of 81729089688 in words is "eighty-one billion, seven hundred twenty-nine million, eighty-nine thousand, six hundred eighty-eight".