81909400320 has 864 divisors, whose sum is σ = 330598195200. Its totient is φ = 18527846400.

The previous prime is 81909400319. The next prime is 81909400333. The reversal of 81909400320 is 2300490918.

It is a super-2 number, since 2×81909400320² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 113920921 + ... + 113921639.

It is an arithmetic number, because the mean of its divisors is an integer number (382636800).

Almost surely, 2^81909400320 is an apocalyptic number.

81909400320 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 81909400320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (165299097600).

81909400320 is an abundant number, since it is smaller than the sum of its proper divisors (248688794880).

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

81909400320 is a wasteful number, since it uses less digits than its factorization.

81909400320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 817 (or 800 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The spelling of 81909400320 in words is "eighty-one billion, nine hundred nine million, four hundred thousand, three hundred twenty".