81680163840 has 528 divisors, whose sum is σ = 326944874880. Its totient is φ = 18634506240.

The previous prime is 81680163839. The next prime is 81680163881. The reversal of 81680163840 is 4836108618.

It is a happy number.

81680163840 is a `hidden beast` number, since 8 + 1 + 6 + 8 + 0 + 1 + 638 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (528).

It is a super-3 number, since 3×81680163840³ (a number of 34 digits) contains 333 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 8612221 + ... + 8621699.

Almost surely, 2^81680163840 is an apocalyptic number.

81680163840 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 81680163840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (163472437440).

81680163840 is an abundant number, since it is smaller than the sum of its proper divisors (245264711040).

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

81680163840 is a wasteful number, since it uses less digits than its factorization.

81680163840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9538 (or 9517 counting only the distinct ones).

The product of its (nonzero) digits is 221184, while the sum is 45.

The spelling of 81680163840 in words is "eighty-one billion, six hundred eighty million, one hundred sixty-three thousand, eight hundred forty".