81681504 has 24 divisors (see below), whose sum is σ = 214414200. Its totient is φ = 27227136.

The previous prime is 81681493. The next prime is 81681511. The reversal of 81681504 is 40518618.

It is a tau number, because it is divible by the number of its divisors (24).

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 3 ways as a sum of consecutive naturals, for example, 425329 + ... + 425520.

It is an arithmetic number, because the mean of its divisors is an integer number (8933925).

Almost surely, 2^81681504 is an apocalyptic number.

It is an amenable number.

81681504 is an abundant number, since it is smaller than the sum of its proper divisors (132732696).

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

81681504 is a wasteful number, since it uses less digits than its factorization.

81681504 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 850862 (or 850854 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 33.

The square root of 81681504 is about 9037.7820287945. The cubic root of 81681504 is about 433.8849390946.

The spelling of 81681504 in words is "eighty-one million, six hundred eighty-one thousand, five hundred four".