81908645696 has 14 divisors (see below), whose sum is σ = 162537468930. Its totient is φ = 40954322816.

The previous prime is 81908645677. The next prime is 81908645773. The reversal of 81908645696 is 69654680918.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 50769102400 + 31139543296 = 225320^2 + 176464^2 .

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, 639911231 + ... + 639911358.

Almost surely, 2^81908645696 is an apocalyptic number.

It is an amenable number.

81908645696 is a deficient number, since it is larger than the sum of its proper divisors (80628823234).

81908645696 is a wasteful number, since it uses less digits than its factorization.

81908645696 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1279822601 (or 1279822591 counting only the distinct ones).

The product of its (nonzero) digits is 22394880, while the sum is 62.

The spelling of 81908645696 in words is "eighty-one billion, nine hundred eight million, six hundred forty-five thousand, six hundred ninety-six".