206401636561 has 2 divisors, whose sum is σ = 206401636562. Its totient is φ = 206401636560.

The previous prime is 206401636477. The next prime is 206401636591. The reversal of 206401636561 is 165636104602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 127934982400 + 78466654161 = 357680^2 + 280119^2 .

It is a cyclic number.

It is not a de Polignac number, because 206401636561 - 2¹⁹ = 206401112273 is a prime.

It is not a weakly prime, because it can be changed into another prime (206401636591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103200818280 + 103200818281.

It is an arithmetic number, because the mean of its divisors is an integer number (103200818281).

Almost surely, 2^206401636561 is an apocalyptic number.

It is an amenable number.

206401636561 is a deficient number, since it is larger than the sum of its proper divisors (1).

206401636561 is an equidigital number, since it uses as much as digits as its factorization.

206401636561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 155520, while the sum is 40.

The spelling of 206401636561 in words is "two hundred six billion, four hundred one million, six hundred thirty-six thousand, five hundred sixty-one".