205405217 has 2 divisors, whose sum is σ = 205405218. Its totient is φ = 205405216.

The previous prime is 205405177. The next prime is 205405243. The reversal of 205405217 is 712504502.

It is an a-pointer prime, because the next prime (205405243) can be obtained adding 205405217 to its sum of digits (26).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 164968336 + 40436881 = 12844^2 + 6359^2 .

It is a cyclic number.

It is not a de Polignac number, because 205405217 - 2⁶ = 205405153 is a prime.

It is not a weakly prime, because it can be changed into another prime (205405267) 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, 102702608 + 102702609.

It is an arithmetic number, because the mean of its divisors is an integer number (102702609).

Almost surely, 2^205405217 is an apocalyptic number.

It is an amenable number.

205405217 is a deficient number, since it is larger than the sum of its proper divisors (1).

205405217 is an equidigital number, since it uses as much as digits as its factorization.

205405217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 205405217 is about 14331.9648687819. The cubic root of 205405217 is about 590.0251037868.

Adding to 205405217 its reverse (712504502), we get a palindrome (917909719).

The spelling of 205405217 in words is "two hundred five million, four hundred five thousand, two hundred seventeen".