28121 has 4 divisors (see below), whose sum is σ = 28644. Its totient is φ = 27600.

The previous prime is 28111. The next prime is 28123. The reversal of 28121 is 12182.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12182 = 2 ⋅6091.

It can be written as a sum of positive squares in 2 ways, for example, as 4096 + 24025 = 64^2 + 155^2 .

It is a cyclic number.

It is not a de Polignac number, because 28121 - 2⁶ = 28057 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 28096 and 28105.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 28121.

It is not an unprimeable number, because it can be changed into a prime (28123) 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, 170 + ... + 291.

It is an arithmetic number, because the mean of its divisors is an integer number (7161).

2²⁸¹²¹ is an apocalyptic number.

It is an amenable number.

28121 is a deficient number, since it is larger than the sum of its proper divisors (523).

28121 is an equidigital number, since it uses as much as digits as its factorization.

28121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522.

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

The square root of 28121 is about 167.6931721925. The cubic root of 28121 is about 30.4095682024.

The spelling of 28121 in words is "twenty-eight thousand, one hundred twenty-one".