81668056 has 8 divisors (see below), whose sum is σ = 153127620. Its totient is φ = 40834024.

The previous prime is 81668047. The next prime is 81668077. The reversal of 81668056 is 65086618.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (8).

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, 5104246 + ... + 5104261.

Almost surely, 2^81668056 is an apocalyptic number.

81668056 is the 4831-st centered heptagonal number.

It is an amenable number.

81668056 is a deficient number, since it is larger than the sum of its proper divisors (71459564).

81668056 is a wasteful number, since it uses less digits than its factorization.

81668056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10208513 (or 10208509 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 40.

The square root of 81668056 is about 9037.0380103217. The cubic root of 81668056 is about 433.8611262581.

The spelling of 81668056 in words is "eighty-one million, six hundred sixty-eight thousand, fifty-six".