205606409 has 2 divisors, whose sum is σ = 205606410. Its totient is φ = 205606408.

The previous prime is 205606403. The next prime is 205606411. The reversal of 205606409 is 904606502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 155550784 + 50055625 = 12472^2 + 7075^2 .

It is a cyclic number.

It is not a de Polignac number, because 205606409 - 2⁴ = 205606393 is a prime.

It is a Sophie Germain prime.

Together with 205606411, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (205606403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102803204 + 102803205.

It is an arithmetic number, because the mean of its divisors is an integer number (102803205).

Almost surely, 2^205606409 is an apocalyptic number.

It is an amenable number.

205606409 is a deficient number, since it is larger than the sum of its proper divisors (1).

205606409 is an equidigital number, since it uses as much as digits as its factorization.

205606409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 205606409 is about 14338.9821465821. The cubic root of 205606409 is about 590.2176818132.

The spelling of 205606409 in words is "two hundred five million, six hundred six thousand, four hundred nine".