81504 has 36 divisors (see below), whose sum is σ = 232596. Its totient is φ = 27072.

The previous prime is 81463. The next prime is 81509. The reversal of 81504 is 40518.

81504 is nontrivially palindromic in base 11.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (18) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81504.

It is not an unprimeable number, because it can be changed into a prime (81509) by changing a digit.

81504 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 147 + ... + 429.

It is an arithmetic number, because the mean of its divisors is an integer number (6461).

2⁸¹⁵⁰⁴ 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 81504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116298).

81504 is an abundant number, since it is smaller than the sum of its proper divisors (151092).

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

81504 is a wasteful number, since it uses less digits than its factorization.

81504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 299 (or 288 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 81504 is about 285.4890540809. The cubic root of 81504 is about 43.3570415959.

It can be divided in two parts, 81 and 504, that added together give a palindrome (585).

The spelling of 81504 in words is "eighty-one thousand, five hundred four".