561809 has 2 divisors, whose sum is σ = 561810. Its totient is φ = 561808.

The previous prime is 561797. The next prime is 561829. The reversal of 561809 is 908165.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 494209 + 67600 = 703^2 + 260^2 .

It is a cyclic number.

It is not a de Polignac number, because 561809 - 2⁸ = 561553 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (561829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 280904 + 280905.

It is an arithmetic number, because the mean of its divisors is an integer number (280905).

2⁵⁶¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

561809 is a deficient number, since it is larger than the sum of its proper divisors (1).

561809 is an equidigital number, since it uses as much as digits as its factorization.

561809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 561809 is about 749.5391917705. The cubic root of 561809 is about 82.5143654201.

The spelling of 561809 in words is "five hundred sixty-one thousand, eight hundred nine".