18409 has 4 divisors (see below), whose sum is σ = 18900. Its totient is φ = 17920.

The previous prime is 18401. The next prime is 18413. The reversal of 18409 is 90481.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5184 + 13225 = 72^2 + 115^2 .

It is a cyclic number.

It is not a de Polignac number, because 18409 - 2³ = 18401 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

18409 is a lucky number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 18409.

It is not an unprimeable number, because it can be changed into a prime (18401) 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, 184 + ... + 265.

It is an arithmetic number, because the mean of its divisors is an integer number (4725).

2¹⁸⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

18409 is a deficient number, since it is larger than the sum of its proper divisors (491).

18409 is an equidigital number, since it uses as much as digits as its factorization.

18409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 490.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 18409 is about 135.6797700470. The cubic root of 18409 is about 26.4044261021.

It can be divided in two parts, 1840 and 9, that added together give a square (1849 = 43²).

The spelling of 18409 in words is "eighteen thousand, four hundred nine".