81959904 has 96 divisors (see below), whose sum is σ = 257473440. Its totient is φ = 25214976.

The previous prime is 81959897. The next prime is 81959929. The reversal of 81959904 is 40995918.

It is a tau number, because it is divible by the number of its divisors (96).

It is a self number, because there is not a number n which added to its sum of digits gives 81959904.

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 15 ways as a sum of consecutive naturals, for example, 7584 + ... + 14880.

It is an arithmetic number, because the mean of its divisors is an integer number (2682015).

Almost surely, 2^81959904 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 81959904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128736720).

81959904 is an abundant number, since it is smaller than the sum of its proper divisors (175513536).

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

81959904 is a wasteful number, since it uses less digits than its factorization.

81959904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7329 (or 7315 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 45.

The square root of 81959904 is about 9053.1709361969. The cubic root of 81959904 is about 434.3773255159.

The spelling of 81959904 in words is "eighty-one million, nine hundred fifty-nine thousand, nine hundred four".