11531581 has 4 divisors (see below), whose sum is σ = 11749212. Its totient is φ = 11313952.

The previous prime is 11531567. The next prime is 11531617. The reversal of 11531581 is 18513511.

11531581 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6200100 + 5331481 = 2490^2 + 2309^2 .

It is a cyclic number.

It is not a de Polignac number, because 11531581 - 2⁵ = 11531549 is a prime.

It is a super-2 number, since 2×11531581² = 265954720719122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11531521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 108736 + ... + 108841.

It is an arithmetic number, because the mean of its divisors is an integer number (2937303).

Almost surely, 2^11531581 is an apocalyptic number.

It is an amenable number.

11531581 is a deficient number, since it is larger than the sum of its proper divisors (217631).

11531581 is an equidigital number, since it uses as much as digits as its factorization.

11531581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217630.

The product of its digits is 600, while the sum is 25.

The square root of 11531581 is about 3395.8181635653. The cubic root of 11531581 is about 225.9243031005.

The spelling of 11531581 in words is "eleven million, five hundred thirty-one thousand, five hundred eighty-one".