28321 has 4 divisors (see below), whose sum is σ = 28672. Its totient is φ = 27972.

The previous prime is 28319. The next prime is 28349. The reversal of 28321 is 12382.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 28321 - 2¹ = 28319 is a prime.

It is an Ulam number.

It is a Duffinian number.

28321 is a lucky number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 28295 and 28304.

It is not an unprimeable number, because it can be changed into a prime (28351) 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, 16 + ... + 238.

It is an arithmetic number, because the mean of its divisors is an integer number (7168).

2²⁸³²¹ is an apocalyptic number.

It is an amenable number.

28321 is a deficient number, since it is larger than the sum of its proper divisors (351).

28321 is a wasteful number, since it uses less digits than its factorization.

28321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350.

The product of its digits is 96, while the sum is 16.

The square root of 28321 is about 168.2884428593. The cubic root of 28321 is about 30.4814901575.

The spelling of 28321 in words is "twenty-eight thousand, three hundred twenty-one".