28421 has 4 divisors (see below), whose sum is σ = 28812. Its totient is φ = 28032.

The previous prime is 28411. The next prime is 28429. The reversal of 28421 is 12482.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 21025 + 7396 = 145^2 + 86^2 .

It is a cyclic number.

It is not a de Polignac number, because 28421 - 2¹⁰ = 27397 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 28421.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 28421.

It is not an unprimeable number, because it can be changed into a prime (28429) 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, 50 + ... + 243.

It is an arithmetic number, because the mean of its divisors is an integer number (7203).

2²⁸⁴²¹ is an apocalyptic number.

It is an amenable number.

28421 is a deficient number, since it is larger than the sum of its proper divisors (391).

28421 is an equidigital number, since it uses as much as digits as its factorization.

28421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 390.

The product of its digits is 128, while the sum is 17.

The square root of 28421 is about 168.5852899870. The cubic root of 28421 is about 30.5173242079.

The spelling of 28421 in words is "twenty-eight thousand, four hundred twenty-one".