18209 has 4 divisors (see below), whose sum is σ = 18480. Its totient is φ = 17940.

The previous prime is 18199. The next prime is 18211. The reversal of 18209 is 90281.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18209 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (18229) 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, 62 + ... + 200.

It is an arithmetic number, because the mean of its divisors is an integer number (4620).

2¹⁸²⁰⁹ is an apocalyptic number.

It is an amenable number.

18209 is a deficient number, since it is larger than the sum of its proper divisors (271).

18209 is a wasteful number, since it uses less digits than its factorization.

18209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 270.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 18209 is about 134.9407277289. The cubic root of 18209 is about 26.3084562725.

The spelling of 18209 in words is "eighteen thousand, two hundred nine".