231531 has 8 divisors (see below), whose sum is σ = 313344. Its totient is φ = 152040.

The previous prime is 231529. The next prime is 231533. The reversal of 231531 is 135132.

It is a happy number.

231531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (231529) and next prime (231533).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 231531 - 2¹ = 231529 is a prime.

It is a super-2 number, since 2×231531² = 107213207922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 231531.

It is not an unprimeable number, because it can be changed into a prime (231533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 331 + ... + 756.

It is an arithmetic number, because the mean of its divisors is an integer number (39168).

2²³¹⁵³¹ is an apocalyptic number.

231531 is a deficient number, since it is larger than the sum of its proper divisors (81813).

231531 is a wasteful number, since it uses less digits than its factorization.

231531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1161.

The product of its digits is 90, while the sum is 15.

The square root of 231531 is about 481.1766827268. The cubic root of 231531 is about 61.4049029319.

Adding to 231531 its reverse (135132), we get a palindrome (366663).

It can be divided in two parts, 2315 and 31, that added together give a triangular number (2346 = T₆₈).

The spelling of 231531 in words is "two hundred thirty-one thousand, five hundred thirty-one".