81599 has 4 divisors (see below), whose sum is σ = 93264. Its totient is φ = 69936.

The previous prime is 81569. The next prime is 81611. The reversal of 81599 is 99518.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81599 - 2⁸ = 81343 is a prime.

It is a Duffinian number.

It is a congruent number.

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

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, 5822 + ... + 5835.

It is an arithmetic number, because the mean of its divisors is an integer number (23316).

2⁸¹⁵⁹⁹ is an apocalyptic number.

81599 is a deficient number, since it is larger than the sum of its proper divisors (11665).

81599 is a wasteful number, since it uses less digits than its factorization.

81599 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11664.

The product of its digits is 3240, while the sum is 32.

The square root of 81599 is about 285.6553867862. The cubic root of 81599 is about 43.3738805227.

The spelling of 81599 in words is "eighty-one thousand, five hundred ninety-nine".