81388689408 has 768 divisors, whose sum is σ = 280687680000. Its totient is φ = 23091609600.

The previous prime is 81388689401. The next prime is 81388689409. The reversal of 81388689408 is 80498688318.

It is a tau number, because it is divible by the number of its divisors (768).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81388689401) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 805828558 + ... + 805828658.

It is an arithmetic number, because the mean of its divisors is an integer number (365478750).

Almost surely, 2^81388689408 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 81388689408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (140343840000).

81388689408 is an abundant number, since it is smaller than the sum of its proper divisors (199298990592).

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

81388689408 is a wasteful number, since it uses less digits than its factorization.

81388689408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223 (or 197 counting only the distinct ones).

The product of its (nonzero) digits is 21233664, while the sum is 63.

The spelling of 81388689408 in words is "eighty-one billion, three hundred eighty-eight million, six hundred eighty-nine thousand, four hundred eight".