205205509 has 2 divisors, whose sum is σ = 205205510. Its totient is φ = 205205508.

The previous prime is 205205501. The next prime is 205205543. The reversal of 205205509 is 905502502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202492900 + 2712609 = 14230^2 + 1647^2 .

It is a cyclic number.

It is not a de Polignac number, because 205205509 - 2³ = 205205501 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205205501) 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 as a sum of consecutive naturals, namely, 102602754 + 102602755.

It is an arithmetic number, because the mean of its divisors is an integer number (102602755).

Almost surely, 2^205205509 is an apocalyptic number.

It is an amenable number.

205205509 is a deficient number, since it is larger than the sum of its proper divisors (1).

205205509 is an equidigital number, since it uses as much as digits as its factorization.

205205509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4500, while the sum is 28.

The square root of 205205509 is about 14324.9959511338. The cubic root of 205205509 is about 589.8338218191.

The spelling of 205205509 in words is "two hundred five million, two hundred five thousand, five hundred nine".