81997976064 has 160 divisors (see below), whose sum is σ = 226819232640. Its totient is φ = 26292224000.

The previous prime is 81997976051. The next prime is 81997976147. The reversal of 81997976064 is 46067979918.

It is a junction number, because it is equal to n+sod(n) for n = 81997975986 and 81997976004.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12513589 + ... + 12520139.

It is an arithmetic number, because the mean of its divisors is an integer number (1417620204).

Almost surely, 2^81997976064 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 81997976064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113409616320).

81997976064 is an abundant number, since it is smaller than the sum of its proper divisors (144821256576).

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

81997976064 is a wasteful number, since it uses less digits than its factorization.

81997976064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6882 (or 6866 counting only the distinct ones).

The product of its (nonzero) digits is 41150592, while the sum is 66.

The spelling of 81997976064 in words is "eighty-one billion, nine hundred ninety-seven million, nine hundred seventy-six thousand, sixty-four".