81399 has 8 divisors (see below), whose sum is σ = 111232. Its totient is φ = 52920.

The previous prime is 81373. The next prime is 81401. The reversal of 81399 is 99318.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-81399 is a prime.

It is a Duffinian number.

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 81399.

It is not an unprimeable number, because it can be changed into a prime (81349) 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 7 ways as a sum of consecutive naturals, for example, 187 + ... + 444.

It is an arithmetic number, because the mean of its divisors is an integer number (13904).

2⁸¹³⁹⁹ is an apocalyptic number.

81399 is a deficient number, since it is larger than the sum of its proper divisors (29833).

81399 is a wasteful number, since it uses less digits than its factorization.

81399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 677.

The product of its digits is 1944, while the sum is 30.

The square root of 81399 is about 285.3050998493. The cubic root of 81399 is about 43.3384149202.

The spelling of 81399 in words is "eighty-one thousand, three hundred ninety-nine".