18981 has 16 divisors (see below), whose sum is σ = 30400. Its totient is φ = 11664.

The previous prime is 18979. The next prime is 19001.

18981 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 18981 - 2¹ = 18979 is a prime.

It is a super-2 number, since 2×18981² = 720556722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

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

It is a Curzon number.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 495 + ... + 531.

It is an arithmetic number, because the mean of its divisors is an integer number (1900).

2¹⁸⁹⁸¹ is an apocalyptic number.

18981 is the 74-th nonagonal number.

It is an amenable number.

18981 is a deficient number, since it is larger than the sum of its proper divisors (11419).

18981 is a wasteful number, since it uses less digits than its factorization.

18981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65 (or 59 counting only the distinct ones).

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

The square root of 18981 is about 137.7715500385. The cubic root of 18981 is about 26.6751188485.

18981 divided by its sum of digits (27) gives a triangular number (703 = T₃₇).

It can be divided in two parts, 18 and 981, that added together give a palindrome (999).

The spelling of 18981 in words is "eighteen thousand, nine hundred eighty-one".