81663981664 has 12 divisors (see below), whose sum is σ = 160775963964. Its totient is φ = 40831990816.

The previous prime is 81663981629. The next prime is 81663981689. The reversal of 81663981664 is 46618936618.

It is a junction number, because it is equal to n+sod(n) for n = 81663981599 and 81663981608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1275999682 + ... + 1275999745.

It is an arithmetic number, because the mean of its divisors is an integer number (13397996997).

Almost surely, 2^81663981664 is an apocalyptic number.

It is an amenable number.

81663981664 is a deficient number, since it is larger than the sum of its proper divisors (79111982300).

81663981664 is a wasteful number, since it uses less digits than its factorization.

81663981664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2551999437 (or 2551999429 counting only the distinct ones).

The product of its digits is 8957952, while the sum is 58.

The spelling of 81663981664 in words is "eighty-one billion, six hundred sixty-three million, nine hundred eighty-one thousand, six hundred sixty-four".