204155521322561 has 2 divisors, whose sum is σ = 204155521322562. Its totient is φ = 204155521322560.

The previous prime is 204155521322531. The next prime is 204155521322579. The reversal of 204155521322561 is 165223125551402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 103202863172161 + 100952658150400 = 10158881^2 + 10047520^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-204155521322561 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (204155521322531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102077760661280 + 102077760661281.

It is an arithmetic number, because the mean of its divisors is an integer number (102077760661281).

Almost surely, 2^{204155521322561} is an apocalyptic number.

It is an amenable number.

204155521322561 is a deficient number, since it is larger than the sum of its proper divisors (1).

204155521322561 is an equidigital number, since it uses as much as digits as its factorization.

204155521322561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720000, while the sum is 44.

Adding to 204155521322561 its reverse (165223125551402), we get a palindrome (369378646873963).

The spelling of 204155521322561 in words is "two hundred four trillion, one hundred fifty-five billion, five hundred twenty-one million, three hundred twenty-two thousand, five hundred sixty-one".