81680520408 has 64 divisors (see below), whose sum is σ = 205992529920. Its totient is φ = 26988393600.

The previous prime is 81680520391. The next prime is 81680520409. The reversal of 81680520408 is 80402508618.

It is a self number, because there is not a number n which added to its sum of digits gives 81680520408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81680520409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3588343 + ... + 3611033.

It is an arithmetic number, because the mean of its divisors is an integer number (3218633280).

Almost surely, 2^81680520408 is an apocalyptic number.

It is an amenable number.

81680520408 is an abundant number, since it is smaller than the sum of its proper divisors (124312009512).

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

81680520408 is a wasteful number, since it uses less digits than its factorization.

81680520408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24008 (or 24004 counting only the distinct ones).

The product of its (nonzero) digits is 122880, while the sum is 42.

The spelling of 81680520408 in words is "eighty-one billion, six hundred eighty million, five hundred twenty thousand, four hundred eight".