205100009 has 2 divisors, whose sum is σ = 205100010. Its totient is φ = 205100008.

The previous prime is 205099987. The next prime is 205100011. The reversal of 205100009 is 900001502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 153834409 + 51265600 = 12403^2 + 7160^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205100009 is a prime.

Together with 205100011, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 205100009.

It is not a weakly prime, because it can be changed into another prime (205100069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102550004 + 102550005.

It is an arithmetic number, because the mean of its divisors is an integer number (102550005).

Almost surely, 2^205100009 is an apocalyptic number.

It is an amenable number.

205100009 is a deficient number, since it is larger than the sum of its proper divisors (1).

205100009 is an equidigital number, since it uses as much as digits as its factorization.

205100009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90, while the sum is 17.

The square root of 205100009 is about 14321.3131032039. The cubic root of 205100009 is about 589.7327229489.

The spelling of 205100009 in words is "two hundred five million, one hundred thousand, nine".