231131209 has 9 divisors (see below), whose sum is σ = 241983399. Its totient is φ = 220747560.

The previous prime is 231131207. The next prime is 231131221. The reversal of 231131209 is 902131132.

The square root of 231131209 is 15203.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 183521209 + 47610000 = 13547^2 + 6900^2 .

It is not a de Polignac number, because 231131209 - 2¹ = 231131207 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 231131209.

It is not an unprimeable number, because it can be changed into a prime (231131207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 349339 + ... + 349999.

Almost surely, 2^231131209 is an apocalyptic number.

231131209 is the 15203-rd square number.

231131209 is the 7602-nd centered octagonal number.

It is an amenable number.

231131209 is a deficient number, since it is larger than the sum of its proper divisors (10852190).

231131209 is an frugal number, since it uses more digits than its factorization.

231131209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1368 (or 684 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 22.

The cubic root of 231131209 is about 613.6953938667.

Multiplying 231131209 by its product of nonzero digits (324), we get a square (74886511716 = 273654²).

The spelling of 231131209 in words is "two hundred thirty-one million, one hundred thirty-one thousand, two hundred nine".