81731904 has 56 divisors (see below), whose sum is σ = 218724480. Its totient is φ = 26932224.

The previous prime is 81731849. The next prime is 81731929. The reversal of 81731904 is 40913718.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14697 + ... + 19479.

Almost surely, 2^81731904 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81731904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109362240).

81731904 is an abundant number, since it is smaller than the sum of its proper divisors (136992576).

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

81731904 is a wasteful number, since it uses less digits than its factorization.

81731904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4887 (or 4877 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 33.

The square root of 81731904 is about 9040.5698935410. The cubic root of 81731904 is about 433.9741608633.

The spelling of 81731904 in words is "eighty-one million, seven hundred thirty-one thousand, nine hundred four".