18221 has 8 divisors (see below), whose sum is σ = 22080. Its totient is φ = 14688.

The previous prime is 18217. The next prime is 18223. The reversal of 18221 is 12281.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18221 - 2² = 18217 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 18196 and 18205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65 + ... + 201.

It is an arithmetic number, because the mean of its divisors is an integer number (2760).

2¹⁸²²¹ is an apocalyptic number.

It is an amenable number.

18221 is a deficient number, since it is larger than the sum of its proper divisors (3859).

18221 is a wasteful number, since it uses less digits than its factorization.

18221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163.

The product of its digits is 32, while the sum is 14.

The square root of 18221 is about 134.9851843722. The cubic root of 18221 is about 26.3142342239.

The spelling of 18221 in words is "eighteen thousand, two hundred twenty-one".