16221 has 4 divisors (see below), whose sum is σ = 21632. Its totient is φ = 10812.

The previous prime is 16217. The next prime is 16223. The reversal of 16221 is 12261.

16221 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 16221 - 2² = 16217 is a prime.

It is an Ulam number.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 16197 and 16206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2701 + ... + 2706.

It is an arithmetic number, because the mean of its divisors is an integer number (5408).

2¹⁶²²¹ is an apocalyptic number.

It is an amenable number.

16221 is a deficient number, since it is larger than the sum of its proper divisors (5411).

16221 is an equidigital number, since it uses as much as digits as its factorization.

16221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5410.

The product of its digits is 24, while the sum is 12.

The square root of 16221 is about 127.3616896873. The cubic root of 16221 is about 25.3139086246.

Adding to 16221 its reverse (12261), we get a palindrome (28482).

The spelling of 16221 in words is "sixteen thousand, two hundred twenty-one".