231509 has 4 divisors (see below), whose sum is σ = 237804. Its totient is φ = 225216.

The previous prime is 231503. The next prime is 231529. The reversal of 231509 is 905132.

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 220900 + 10609 = 470^2 + 103^2 .

It is a cyclic number.

It is not a de Polignac number, because 231509 - 2⁴ = 231493 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231503) 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, 3092 + ... + 3165.

It is an arithmetic number, because the mean of its divisors is an integer number (59451).

2²³¹⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

231509 is a deficient number, since it is larger than the sum of its proper divisors (6295).

231509 is an equidigital number, since it uses as much as digits as its factorization.

231509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6294.

The product of its (nonzero) digits is 270, while the sum is 20.

The square root of 231509 is about 481.1538215581. The cubic root of 231509 is about 61.4029579791.

The spelling of 231509 in words is "two hundred thirty-one thousand, five hundred nine".