27581 has 2 divisors, whose sum is σ = 27582. Its totient is φ = 27580.

The previous prime is 27551. The next prime is 27583. The reversal of 27581 is 18572.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27556 + 25 = 166^2 + 5^2 .

It is a cyclic number.

It is not a de Polignac number, because 27581 - 2¹⁰ = 26557 is a prime.

It is a super-2 number, since 2×27581² = 1521423122, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 27583, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (27583) 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 as a sum of consecutive naturals, namely, 13790 + 13791.

It is an arithmetic number, because the mean of its divisors is an integer number (13791).

2²⁷⁵⁸¹ is an apocalyptic number.

It is an amenable number.

27581 is a deficient number, since it is larger than the sum of its proper divisors (1).

27581 is an equidigital number, since it uses as much as digits as its factorization.

27581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 560, while the sum is 23.

The square root of 27581 is about 166.0752841334. The cubic root of 27581 is about 30.2136598878.

Subtracting from 27581 its reverse (18572), we obtain a palindrome (9009).

The spelling of 27581 in words is "twenty-seven thousand, five hundred eighty-one".