205806 has 8 divisors (see below), whose sum is σ = 411624. Its totient is φ = 68600.

The previous prime is 205783. The next prime is 205817. The reversal of 205806 is 608502.

It is a happy number.

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

205806 is an admirable number.

It is a super-2 number, since 2×205806² = 84712219272, which contains 22 as substring.

It is a Curzon 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 205806.

It is an unprimeable number.

205806 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 17145 + ... + 17156.

It is an arithmetic number, because the mean of its divisors is an integer number (51453).

2²⁰⁵⁸⁰⁶ is an apocalyptic number.

205806 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

205806 is a wasteful number, since it uses less digits than its factorization.

205806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34306.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 205806 is about 453.6584618411. The cubic root of 205806 is about 59.0408603293.

The spelling of 205806 in words is "two hundred five thousand, eight hundred six".