231205509 has 24 divisors (see below), whose sum is σ = 364567840. Its totient is φ = 146021616.

The previous prime is 231205477. The next prime is 231205523. The reversal of 231205509 is 905502132.

It is not a de Polignac number, because 231205509 - 2⁵ = 231205477 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231205589) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20422 + ... + 29655.

Almost surely, 2^231205509 is an apocalyptic number.

It is an amenable number.

231205509 is a deficient number, since it is larger than the sum of its proper divisors (133362331).

231205509 is an equidigital number, since it uses as much as digits as its factorization.

231205509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50111 (or 50099 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 27.

The square root of 231205509 is about 15205.4434003090. The cubic root of 231205509 is about 613.7611468256.

The spelling of 231205509 in words is "two hundred thirty-one million, two hundred five thousand, five hundred nine".