231581 has 4 divisors (see below), whose sum is σ = 264672. Its totient is φ = 198492.

The previous prime is 231571. The next prime is 231589. The reversal of 231581 is 185132.

231581 is digitally balanced in base 2, 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, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 231581 - 2¹⁴ = 215197 is a prime.

It is a super-2 number, since 2×231581² = 107259519122, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231589) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16535 + ... + 16548.

It is an arithmetic number, because the mean of its divisors is an integer number (66168).

2²³¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

231581 is a deficient number, since it is larger than the sum of its proper divisors (33091).

231581 is an equidigital number, since it uses as much as digits as its factorization.

231581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33090.

The product of its digits is 240, while the sum is 20.

The square root of 231581 is about 481.2286358894. The cubic root of 231581 is about 61.4093228212.

It can be divided in two parts, 23 and 1581, that multiplied together give a palindrome (36363).

The spelling of 231581 in words is "two hundred thirty-one thousand, five hundred eighty-one".