205564661 has 2 divisors, whose sum is σ = 205564662. Its totient is φ = 205564660.

The previous prime is 205564657. The next prime is 205564703. The reversal of 205564661 is 166465502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 144240100 + 61324561 = 12010^2 + 7831^2 .

It is a cyclic number.

It is not a de Polignac number, because 205564661 - 2² = 205564657 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205564651) 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, 102782330 + 102782331.

It is an arithmetic number, because the mean of its divisors is an integer number (102782331).

Almost surely, 2^205564661 is an apocalyptic number.

It is an amenable number.

205564661 is a deficient number, since it is larger than the sum of its proper divisors (1).

205564661 is an equidigital number, since it uses as much as digits as its factorization.

205564661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43200, while the sum is 35.

The square root of 205564661 is about 14337.5263208128. The cubic root of 205564661 is about 590.1777315740.

The spelling of 205564661 in words is "two hundred five million, five hundred sixty-four thousand, six hundred sixty-one".