581561 has 4 divisors (see below), whose sum is σ = 589824. Its totient is φ = 573300.

The previous prime is 581557. The next prime is 581573. The reversal of 581561 is 165185.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 165185 = 5 ⋅33037.

It is a cyclic number.

It is not a de Polignac number, because 581561 - 2² = 581557 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 581561.

It is not an unprimeable number, because it can be changed into a prime (581521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4025 + ... + 4166.

It is an arithmetic number, because the mean of its divisors is an integer number (147456).

2⁵⁸¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

581561 is a deficient number, since it is larger than the sum of its proper divisors (8263).

581561 is an equidigital number, since it uses as much as digits as its factorization.

581561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8262.

The product of its digits is 1200, while the sum is 26.

The square root of 581561 is about 762.6014686584. The cubic root of 581561 is about 83.4702584505.

The spelling of 581561 in words is "five hundred eighty-one thousand, five hundred sixty-one".