131209 has 4 divisors (see below), whose sum is σ = 141316. Its totient is φ = 121104.

The previous prime is 131203. The next prime is 131213. The reversal of 131209 is 902131.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 902131 = 31 ⋅29101.

It can be written as a sum of positive squares in 2 ways, for example, as 41209 + 90000 = 203^2 + 300^2 .

It is a cyclic number.

It is not a de Polignac number, because 131209 - 2¹³ = 123017 is a prime.

It is a Duffinian number.

131209 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 131192 and 131201.

It is not an unprimeable number, because it can be changed into a prime (131203) 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, 5034 + ... + 5059.

It is an arithmetic number, because the mean of its divisors is an integer number (35329).

2¹³¹²⁰⁹ is an apocalyptic number.

It is an amenable number.

131209 is a deficient number, since it is larger than the sum of its proper divisors (10107).

131209 is a wasteful number, since it uses less digits than its factorization.

131209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10106.

The product of its (nonzero) digits is 54, while the sum is 16.

The square root of 131209 is about 362.2278288591. The cubic root of 131209 is about 50.8145255753.

The spelling of 131209 in words is "one hundred thirty-one thousand, two hundred nine".