205663921 has 2 divisors, whose sum is σ = 205663922. Its totient is φ = 205663920.

The previous prime is 205663897. The next prime is 205663949. The reversal of 205663921 is 129366502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204175521 + 1488400 = 14289^2 + 1220^2 .

It is a cyclic number.

It is not a de Polignac number, because 205663921 - 2¹⁹ = 205139633 is a prime.

It is not a weakly prime, because it can be changed into another prime (205663981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102831960 + 102831961.

It is an arithmetic number, because the mean of its divisors is an integer number (102831961).

Almost surely, 2^205663921 is an apocalyptic number.

It is an amenable number.

205663921 is a deficient number, since it is larger than the sum of its proper divisors (1).

205663921 is an equidigital number, since it uses as much as digits as its factorization.

205663921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19440, while the sum is 34.

The square root of 205663921 is about 14340.9874485685. The cubic root of 205663921 is about 590.2727083645.

The spelling of 205663921 in words is "two hundred five million, six hundred sixty-three thousand, nine hundred twenty-one".