809581 has 2 divisors, whose sum is σ = 809582. Its totient is φ = 809580.

The previous prime is 809579. The next prime is 809587. The reversal of 809581 is 185908.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 443556 + 366025 = 666^2 + 605^2 .

It is a cyclic number.

It is not a de Polignac number, because 809581 - 2¹ = 809579 is a prime.

It is a super-2 number, since 2×809581² = 1310842791122, which contains 22 as substring.

Together with 809579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (809587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404790 + 404791.

It is an arithmetic number, because the mean of its divisors is an integer number (404791).

2⁸⁰⁹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

809581 is a deficient number, since it is larger than the sum of its proper divisors (1).

809581 is an equidigital number, since it uses as much as digits as its factorization.

809581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2880, while the sum is 31.

The square root of 809581 is about 899.7671921114. The cubic root of 809581 is about 93.2008991913.

The spelling of 809581 in words is "eight hundred nine thousand, five hundred eighty-one".