205605 has 16 divisors (see below), whose sum is σ = 365760. Its totient is φ = 109584.

The previous prime is 205603. The next prime is 205607. The reversal of 205605 is 506502.

It is an interprime number because it is at equal distance from previous prime (205603) and next prime (205607).

It is not a de Polignac number, because 205605 - 2¹ = 205603 is a prime.

It is an Ulam number.

It is a Curzon number.

205605 is a lucky number.

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 15 ways as a sum of consecutive naturals, for example, 627 + ... + 896.

It is an arithmetic number, because the mean of its divisors is an integer number (22860).

2²⁰⁵⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

205605 is a deficient number, since it is larger than the sum of its proper divisors (160155).

205605 is a wasteful number, since it uses less digits than its factorization.

205605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1537 (or 1531 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 18.

The square root of 205605 is about 453.4368754303. The cubic root of 205605 is about 59.0216333576.

It can be divided in two parts, 20 and 5605, that added together give a square (5625 = 75²).

The spelling of 205605 in words is "two hundred five thousand, six hundred five".