81665472 has 56 divisors (see below), whose sum is σ = 246944896. Its totient is φ = 23332608.

The previous prime is 81665447. The next prime is 81665483. The reversal of 81665472 is 27456618.

It is a tau number, because it is divible by the number of its divisors (56).

It is a self number, because there is not a number n which added to its sum of digits gives 81665472.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29038 + ... + 31725.

Almost surely, 2^81665472 is an apocalyptic number.

It is an amenable number.

81665472 is an abundant number, since it is smaller than the sum of its proper divisors (165279424).

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

81665472 is a wasteful number, since it uses less digits than its factorization.

81665472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60785 (or 60775 counting only the distinct ones).

The product of its digits is 80640, while the sum is 39.

The square root of 81665472 is about 9036.8950419931. The cubic root of 81665472 is about 433.8565503810.

The spelling of 81665472 in words is "eighty-one million, six hundred sixty-five thousand, four hundred seventy-two".