205565 has 4 divisors (see below), whose sum is σ = 246684. Its totient is φ = 164448.

The previous prime is 205559. The next prime is 205589. The reversal of 205565 is 565502.

205565 = T₁₅₈ + T₁₅₉ + ... + T₁₇₂.

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 119716 + 85849 = 346^2 + 293^2 .

It is a cyclic number.

It is not a de Polignac number, because 205565 - 2⁴ = 205549 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 205565.

It is a congruent number.

It is an unprimeable 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, 20552 + ... + 20561.

It is an arithmetic number, because the mean of its divisors is an integer number (61671).

2²⁰⁵⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

205565 is a deficient number, since it is larger than the sum of its proper divisors (41119).

205565 is an equidigital number, since it uses as much as digits as its factorization.

205565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41118.

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 205565 is about 453.3927657120. The cubic root of 205565 is about 59.0178055998.

The spelling of 205565 in words is "two hundred five thousand, five hundred sixty-five".