28021 has 4 divisors (see below), whose sum is σ = 32032. Its totient is φ = 24012.

The previous prime is 28019. The next prime is 28027. The reversal of 28021 is 12082.

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 a cyclic number.

It is not a de Polignac number, because 28021 - 2¹ = 28019 is a prime.

28021 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 27992 and 28010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28027) 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, 1995 + ... + 2008.

It is an arithmetic number, because the mean of its divisors is an integer number (8008).

2²⁸⁰²¹ is an apocalyptic number.

It is an amenable number.

28021 is a deficient number, since it is larger than the sum of its proper divisors (4011).

28021 is an equidigital number, since it uses as much as digits as its factorization.

28021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4010.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 28021 is about 167.3947430477. The cubic root of 28021 is about 30.3734792941.

The spelling of 28021 in words is "twenty-eight thousand, twenty-one".