18811 has 4 divisors (see below), whose sum is σ = 20272. Its totient is φ = 17352.

The previous prime is 18803. The next prime is 18839. The reversal of 18811 is 11881.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11881 = 109².

It is a cyclic number.

It is not a de Polignac number, because 18811 - 2³ = 18803 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 12 and base 13.

It is a zygodrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (18211) 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, 711 + ... + 736.

It is an arithmetic number, because the mean of its divisors is an integer number (5068).

2¹⁸⁸¹¹ is an apocalyptic number.

18811 is a deficient number, since it is larger than the sum of its proper divisors (1461).

18811 is a wasteful number, since it uses less digits than its factorization.

18811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1460.

The product of its digits is 64, while the sum is 19.

The square root of 18811 is about 137.1531990148. The cubic root of 18811 is about 26.5952428978.

The spelling of 18811 in words is "eighteen thousand, eight hundred eleven".