205643609 has 2 divisors, whose sum is σ = 205643610. Its totient is φ = 205643608.

The previous prime is 205643597. The next prime is 205643639. The reversal of 205643609 is 906346502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 168091225 + 37552384 = 12965^2 + 6128^2 .

It is a cyclic number.

It is not a de Polignac number, because 205643609 - 2¹⁶ = 205578073 is a prime.

It is not a weakly prime, because it can be changed into another prime (205643639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102821804 + 102821805.

It is an arithmetic number, because the mean of its divisors is an integer number (102821805).

Almost surely, 2^205643609 is an apocalyptic number.

It is an amenable number.

205643609 is a deficient number, since it is larger than the sum of its proper divisors (1).

205643609 is an equidigital number, since it uses as much as digits as its factorization.

205643609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 35.

The square root of 205643609 is about 14340.2792511164. The cubic root of 205643609 is about 590.2532753434.

The spelling of 205643609 in words is "two hundred five million, six hundred forty-three thousand, six hundred nine".