18909 has 12 divisors (see below), whose sum is σ = 29952. Its totient is φ = 11400.

The previous prime is 18899. The next prime is 18911. The reversal of 18909 is 90981.

It is not a de Polignac number, because 18909 - 2⁹ = 18397 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18919) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4 + ... + 194.

It is an arithmetic number, because the mean of its divisors is an integer number (2496).

2¹⁸⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

18909 is a deficient number, since it is larger than the sum of its proper divisors (11043).

18909 is a wasteful number, since it uses less digits than its factorization.

18909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208 (or 205 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 18909 is about 137.5099996364. The cubic root of 18909 is about 26.6413474956.

The spelling of 18909 in words is "eighteen thousand, nine hundred nine".