18009 has 16 divisors (see below), whose sum is σ = 28800. Its totient is φ = 11088.

The previous prime is 17989. The next prime is 18013. The reversal of 18009 is 90081.

It is not a de Polignac number, because 18009 - 2⁵ = 17977 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 17982 and 18000.

It is not an unprimeable number, because it can be changed into a prime (18049) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 607 + ... + 635.

It is an arithmetic number, because the mean of its divisors is an integer number (1800).

2¹⁸⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

18009 is a deficient number, since it is larger than the sum of its proper divisors (10791).

18009 is a wasteful number, since it uses less digits than its factorization.

18009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61 (or 55 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The square root of 18009 is about 134.1976154781. The cubic root of 18009 is about 26.2117811166.

Adding to 18009 its product of nonzero digits (72), we get a palindrome (18081).

The spelling of 18009 in words is "eighteen thousand, nine".