81904 has 10 divisors (see below), whose sum is σ = 158720.
Its totient is φ = 40944.
The previous prime is 81901. The next prime is 81919. The reversal of 81904 is 40918.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (81901) by changing a digit.
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 as a sum of consecutive naturals, namely, 2544 + ... + 2575.
It is an arithmetic number, because the mean of its divisors is an integer number (15872).
281904 is an apocalyptic number.
It is an amenable number.
81904 is a deficient number, since it is larger than the sum of its proper divisors (76816).
81904 is a wasteful number, since it uses less digits than its factorization.
81904 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 5127 (or 5121 counting only the distinct ones).
The product of its (nonzero) digits is 288, while the sum is 22.
The square root of 81904 is about 286.1887489053.
The cubic root of 81904 is about 43.4278541631.
The spelling of 81904 in words is "eighty-one thousand, nine hundred four".