205520509 has 2 divisors, whose sum is σ = 205520510. Its totient is φ = 205520508.

The previous prime is 205520507. The next prime is 205520537. The reversal of 205520509 is 905025502.

It is an a-pointer prime, because the next prime (205520537) can be obtained adding 205520509 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 119902500 + 85618009 = 10950^2 + 9253^2 .

It is a cyclic number.

It is not a de Polignac number, because 205520509 - 2¹ = 205520507 is a prime.

Together with 205520507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205520501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102760254 + 102760255.

It is an arithmetic number, because the mean of its divisors is an integer number (102760255).

Almost surely, 2^205520509 is an apocalyptic number.

It is an amenable number.

205520509 is a deficient number, since it is larger than the sum of its proper divisors (1).

205520509 is an equidigital number, since it uses as much as digits as its factorization.

205520509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4500, while the sum is 28.

The square root of 205520509 is about 14335.9865025048. The cubic root of 205520509 is about 590.1354749707.

The spelling of 205520509 in words is "two hundred five million, five hundred twenty thousand, five hundred nine".