205001561 has 2 divisors, whose sum is σ = 205001562. Its totient is φ = 205001560.

The previous prime is 205001527. The next prime is 205001579. The reversal of 205001561 is 165100502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 135862336 + 69139225 = 11656^2 + 8315^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205001561 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_11340551 and since 205001561 and 11340551 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 (205001581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102500780 + 102500781.

It is an arithmetic number, because the mean of its divisors is an integer number (102500781).

Almost surely, 2^205001561 is an apocalyptic number.

It is an amenable number.

205001561 is a deficient number, since it is larger than the sum of its proper divisors (1).

205001561 is an equidigital number, since it uses as much as digits as its factorization.

205001561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 205001561 is about 14317.8755756572. The cubic root of 205001561 is about 589.6383506162.

The spelling of 205001561 in words is "two hundred five million, one thousand, five hundred sixty-one".