28181 has 2 divisors, whose sum is σ = 28182. Its totient is φ = 28180.

The previous prime is 28163. The next prime is 28183. The reversal of 28181 is 18182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27556 + 625 = 166^2 + 25^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28181 is a prime.

It is a super-2 number, since 2×28181² = 1588337522, which contains 22 as substring.

Together with 28183, it forms a pair of twin primes.

It is a Chen prime.

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 28181.

It is not a weakly prime, because it can be changed into another prime (28183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14090 + 14091.

It is an arithmetic number, because the mean of its divisors is an integer number (14091).

2²⁸¹⁸¹ is an apocalyptic number.

It is an amenable number.

28181 is a deficient number, since it is larger than the sum of its proper divisors (1).

28181 is an equidigital number, since it uses as much as digits as its factorization.

28181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 128, while the sum is 20.

The square root of 28181 is about 167.8719750286. The cubic root of 28181 is about 30.4311804965.

Subtracting from 28181 its reverse (18182), we obtain a palindrome (9999).

The spelling of 28181 in words is "twenty-eight thousand, one hundred eighty-one".