81859 has 4 divisors (see below), whose sum is σ = 82720. Its totient is φ = 81000.

The previous prime is 81853. The next prime is 81869. The reversal of 81859 is 95818.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 81859 - 2¹¹ = 79811 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81859.

It is not an unprimeable number, because it can be changed into a prime (81853) 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 in 3 ways as a sum of consecutive naturals, for example, 267 + ... + 484.

It is an arithmetic number, because the mean of its divisors is an integer number (20680).

2⁸¹⁸⁵⁹ is an apocalyptic number.

81859 is a deficient number, since it is larger than the sum of its proper divisors (861).

81859 is a wasteful number, since it uses less digits than its factorization.

81859 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 860.

The product of its digits is 2880, while the sum is 31.

The square root of 81859 is about 286.1101186606. The cubic root of 81859 is about 43.4198992750.

The spelling of 81859 in words is "eighty-one thousand, eight hundred fifty-nine".