205609 has 4 divisors (see below), whose sum is σ = 211204. Its totient is φ = 200016.

The previous prime is 205607. The next prime is 205619. The reversal of 205609 is 906502.

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

It can be written as a sum of positive squares in 2 ways, for example, as 189225 + 16384 = 435^2 + 128^2 .

It is a cyclic number.

It is not a de Polignac number, because 205609 - 2¹ = 205607 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 205609.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205603) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2742 + ... + 2815.

It is an arithmetic number, because the mean of its divisors is an integer number (52801).

2²⁰⁵⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

205609 is a deficient number, since it is larger than the sum of its proper divisors (5595).

205609 is an equidigital number, since it uses as much as digits as its factorization.

205609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5594.

The product of its (nonzero) digits is 540, while the sum is 22.

The square root of 205609 is about 453.4412861661. The cubic root of 205609 is about 59.0220161061.

Adding to 205609 its reverse (906502), we get a palindrome (1112111).

The spelling of 205609 in words is "two hundred five thousand, six hundred nine".