18809 has 4 divisors (see below), whose sum is σ = 21504. Its totient is φ = 16116.

The previous prime is 18803. The next prime is 18839. The reversal of 18809 is 90881.

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 an emirpimes, since its reverse is a distinct semiprime: 90881 = 7 ⋅12983.

It is a cyclic number.

It is not a de Polignac number, because 18809 - 2⁴ = 18793 is a prime.

It is a Curzon 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 (18803) 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, 1337 + ... + 1350.

It is an arithmetic number, because the mean of its divisors is an integer number (5376).

2¹⁸⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

18809 is a deficient number, since it is larger than the sum of its proper divisors (2695).

18809 is an equidigital number, since it uses as much as digits as its factorization.

18809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2694.

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 18809 is about 137.1459077042. The cubic root of 18809 is about 26.5943003221.

The spelling of 18809 in words is "eighteen thousand, eight hundred nine".