205142309 has 2 divisors, whose sum is σ = 205142310. Its totient is φ = 205142308.

The previous prime is 205142279. The next prime is 205142321. The reversal of 205142309 is 903241502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 134212225 + 70930084 = 11585^2 + 8422^2 .

It is a cyclic number.

It is not a de Polignac number, because 205142309 - 2²⁰ = 204093733 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205142369) 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, 102571154 + 102571155.

It is an arithmetic number, because the mean of its divisors is an integer number (102571155).

Almost surely, 2^205142309 is an apocalyptic number.

It is an amenable number.

205142309 is a deficient number, since it is larger than the sum of its proper divisors (1).

205142309 is an equidigital number, since it uses as much as digits as its factorization.

205142309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 205142309 is about 14322.7898469537. The cubic root of 205142309 is about 589.7732624879.

The spelling of 205142309 in words is "two hundred five million, one hundred forty-two thousand, three hundred nine".