205666217 has 2 divisors, whose sum is σ = 205666218. Its totient is φ = 205666216.

The previous prime is 205666193. The next prime is 205666229. The reversal of 205666217 is 712666502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 205664281 + 1936 = 14341^2 + 44^2 .

It is a cyclic number.

It is not a de Polignac number, because 205666217 - 2⁸ = 205665961 is a prime.

It is equal to p_11375198 and since 205666217 and 11375198 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (205666277) 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, 102833108 + 102833109.

It is an arithmetic number, because the mean of its divisors is an integer number (102833109).

Almost surely, 2^205666217 is an apocalyptic number.

It is an amenable number.

205666217 is a deficient number, since it is larger than the sum of its proper divisors (1).

205666217 is an equidigital number, since it uses as much as digits as its factorization.

205666217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30240, while the sum is 35.

The square root of 205666217 is about 14341.0674986209. The cubic root of 205666217 is about 590.2749049272.

The spelling of 205666217 in words is "two hundred five million, six hundred sixty-six thousand, two hundred seventeen".