21589 has 2 divisors, whose sum is σ = 21590. Its totient is φ = 21588.

The previous prime is 21587. The next prime is 21599. The reversal of 21589 is 98512.

21589 is nontrivially palindromic in base 8.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18225 + 3364 = 135^2 + 58^2 .

It is a cyclic number.

It is not a de Polignac number, because 21589 - 2¹ = 21587 is a prime.

Together with 21587, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10794 + 10795.

It is an arithmetic number, because the mean of its divisors is an integer number (10795).

2²¹⁵⁸⁹ is an apocalyptic number.

It is an amenable number.

21589 is a deficient number, since it is larger than the sum of its proper divisors (1).

21589 is an equidigital number, since it uses as much as digits as its factorization.

21589 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 25.

The square root of 21589 is about 146.9319570413. The cubic root of 21589 is about 27.8448046548.

The spelling of 21589 in words is "twenty-one thousand, five hundred eighty-nine".