18281 has 4 divisors (see below), whose sum is σ = 18564. Its totient is φ = 18000.

The previous prime is 18269. The next prime is 18287.

18281 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 8281 + 10000 = 91^2 + 100^2 .

It is a cyclic number.

It is not a de Polignac number, because 18281 - 2⁶ = 18217 is a prime.

It is a super-2 number, since 2×18281² = 668389922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 18281.

It is not an unprimeable number, because it can be changed into a prime (18287) 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, 11 + ... + 191.

It is an arithmetic number, because the mean of its divisors is an integer number (4641).

2¹⁸²⁸¹ is an apocalyptic number.

It is an amenable number.

18281 is a deficient number, since it is larger than the sum of its proper divisors (283).

18281 is a wasteful number, since it uses less digits than its factorization.

18281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282.

The product of its digits is 128, while the sum is 20.

The square root of 18281 is about 135.2072483264. The cubic root of 18281 is about 26.3430859922.

The spelling of 18281 in words is "eighteen thousand, two hundred eighty-one".