131809 has 4 divisors (see below), whose sum is σ = 133380. Its totient is φ = 130240.

The previous prime is 131797. The next prime is 131837. The reversal of 131809 is 908131.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 908131 = 7 ⋅129733.

It can be written as a sum of positive squares in 2 ways, for example, as 40000 + 91809 = 200^2 + 303^2 .

It is a cyclic number.

It is not a de Polignac number, because 131809 - 2⁵ = 131777 is a prime.

It is a super-2 number, since 2×131809² = 34747224962, which contains 22 as substring.

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 131809.

It is not an unprimeable number, because it can be changed into a prime (131839) 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, 652 + ... + 829.

It is an arithmetic number, because the mean of its divisors is an integer number (33345).

2¹³¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

131809 is a deficient number, since it is larger than the sum of its proper divisors (1571).

131809 is an equidigital number, since it uses as much as digits as its factorization.

131809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1570.

The product of its (nonzero) digits is 216, while the sum is 22.

The square root of 131809 is about 363.0550922381. The cubic root of 131809 is about 50.8918636632.

The spelling of 131809 in words is "one hundred thirty-one thousand, eight hundred nine".