18891 has 6 divisors (see below), whose sum is σ = 27300. Its totient is φ = 12588.

The previous prime is 18869. The next prime is 18899. The reversal of 18891 is 19881.

18891 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 18891 - 2⁵ = 18859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18899) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1041 + ... + 1058.

It is an arithmetic number, because the mean of its divisors is an integer number (4550).

2¹⁸⁸⁹¹ is an apocalyptic number.

18891 is a deficient number, since it is larger than the sum of its proper divisors (8409).

18891 is a wasteful number, since it uses less digits than its factorization.

18891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2105 (or 2102 counting only the distinct ones).

The product of its digits is 576, while the sum is 27.

The square root of 18891 is about 137.4445342675. Note that the first 3 decimals coincide. The cubic root of 18891 is about 26.6328912667.

Subtracting 18891 from its reverse (19881), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 18 and 891, that added together give a palindrome (909).

The spelling of 18891 in words is "eighteen thousand, eight hundred ninety-one".