561806561 has 2 divisors, whose sum is σ = 561806562. Its totient is φ = 561806560.

The previous prime is 561806503. The next prime is 561806563. The reversal of 561806561 is 165608165.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 481363600 + 80442961 = 21940^2 + 8969^2 .

It is a cyclic number.

It is not a de Polignac number, because 561806561 - 2¹⁰ = 561805537 is a prime.

It is a super-2 number, since 2×561806561² = 631253223965293442, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 561806563, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (561806563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 280903280 + 280903281.

It is an arithmetic number, because the mean of its divisors is an integer number (280903281).

Almost surely, 2^561806561 is an apocalyptic number.

It is an amenable number.

561806561 is a deficient number, since it is larger than the sum of its proper divisors (1).

561806561 is an equidigital number, since it uses as much as digits as its factorization.

561806561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 43200, while the sum is 38.

The square root of 561806561 is about 23702.4589652635. The cubic root of 561806561 is about 825.1424601248.

The spelling of 561806561 in words is "five hundred sixty-one million, eight hundred six thousand, five hundred sixty-one".