205865 has 16 divisors (see below), whose sum is σ = 285120. Its totient is φ = 141120.

The previous prime is 205847. The next prime is 205879. The reversal of 205865 is 568502.

205865 = 20² + 21² + ... + 85².

It is not a de Polignac number, because 205865 - 2¹² = 201769 is a prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 205865.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 947 + ... + 1143.

It is an arithmetic number, because the mean of its divisors is an integer number (17820).

2²⁰⁵⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

205865 is a deficient number, since it is larger than the sum of its proper divisors (79255).

205865 is a wasteful number, since it uses less digits than its factorization.

205865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 205865 is about 453.7234840737. The cubic root of 205865 is about 59.0465016904.

It can be divided in two parts, 20 and 5865, that added together give a palindrome (5885).

The spelling of 205865 in words is "two hundred five thousand, eight hundred sixty-five".