205735809 has 16 divisors (see below), whose sum is σ = 285409280. Its totient is φ = 131680080.

The previous prime is 205735801. The next prime is 205735837. The reversal of 205735809 is 908537502.

It is not a de Polignac number, because 205735809 - 2³ = 205735801 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205735801) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 3102 + ... + 20520.

It is an arithmetic number, because the mean of its divisors is an integer number (17838080).

Almost surely, 2^205735809 is an apocalyptic number.

It is an amenable number.

205735809 is a deficient number, since it is larger than the sum of its proper divisors (79673471).

205735809 is a wasteful number, since it uses less digits than its factorization.

205735809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17580.

The product of its (nonzero) digits is 75600, while the sum is 39.

The square root of 205735809 is about 14343.4936120877. The cubic root of 205735809 is about 590.3414752167.

The spelling of 205735809 in words is "two hundred five million, seven hundred thirty-five thousand, eight hundred nine".