205090309 has 2 divisors, whose sum is σ = 205090310. Its totient is φ = 205090308.

The previous prime is 205090279. The next prime is 205090373. The reversal of 205090309 is 903090502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 116316225 + 88774084 = 10785^2 + 9422^2 .

It is a cyclic number.

It is not a de Polignac number, because 205090309 - 2⁷ = 205090181 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205090709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102545154 + 102545155.

It is an arithmetic number, because the mean of its divisors is an integer number (102545155).

Almost surely, 2^205090309 is an apocalyptic number.

It is an amenable number.

205090309 is a deficient number, since it is larger than the sum of its proper divisors (1).

205090309 is an equidigital number, since it uses as much as digits as its factorization.

205090309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2430, while the sum is 28.

The square root of 205090309 is about 14320.9744431027. The cubic root of 205090309 is about 589.7234258624.

The spelling of 205090309 in words is "two hundred five million, ninety thousand, three hundred nine".