28091 has 4 divisors (see below), whose sum is σ = 32112. Its totient is φ = 24072.

The previous prime is 28087. The next prime is 28097. The reversal of 28091 is 19082.

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

It is a cyclic number.

It is not a de Polignac number, because 28091 - 2² = 28087 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 28091.

It is not an unprimeable number, because it can be changed into a prime (28097) 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, 2000 + ... + 2013.

It is an arithmetic number, because the mean of its divisors is an integer number (8028).

2²⁸⁰⁹¹ is an apocalyptic number.

28091 is a deficient number, since it is larger than the sum of its proper divisors (4021).

28091 is an equidigital number, since it uses as much as digits as its factorization.

28091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4020.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 28091 is about 167.6036992432. The cubic root of 28091 is about 30.3987505257.

Subtracting from 28091 its reverse (19082), we obtain a palindrome (9009).

The spelling of 28091 in words is "twenty-eight thousand, ninety-one".