11809 has 6 divisors (see below), whose sum is σ = 13794. Its totient is φ = 10080.

The previous prime is 11807. The next prime is 11813. The reversal of 11809 is 90811.

11809 is nontrivially palindromic in base 9.

11809 is an esthetic number in base 3, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in only one way, i.e., 11025 + 784 = 105^2 + 28^2 .

It is not a de Polignac number, because 11809 - 2¹ = 11807 is a prime.

It is a Duffinian number.

11809 is an undulating number in base 9.

It is not an unprimeable number, because it can be changed into a prime (11801) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 72 + ... + 169.

It is an arithmetic number, because the mean of its divisors is an integer number (2299).

2¹¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

11809 is a deficient number, since it is larger than the sum of its proper divisors (1985).

11809 is an equidigital number, since it uses as much as digits as its factorization.

11809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255 (or 248 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 11809 is about 108.6692228738. The cubic root of 11809 is about 22.7721677417.

Adding to 11809 its product of nonzero digits (72), we get a square (11881 = 109²).

It can be divided in two parts, 11 and 809, that added together give a triangular number (820 = T₄₀).

The spelling of 11809 in words is "eleven thousand, eight hundred nine".