21189 has 8 divisors (see below), whose sum is σ = 32320. Its totient is φ = 12096.

The previous prime is 21187. The next prime is 21191. The reversal of 21189 is 98112.

It is an interprime number because it is at equal distance from previous prime (21187) and next prime (21191).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21189 - 2¹ = 21187 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1009 = 21189 / (2 + 1 + 1 + 8 + 9).

It is a Duffinian number.

21189 is a modest number, since divided by 189 gives 21 as remainder.

It is a Curzon number.

21189 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21187) 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 in 7 ways as a sum of consecutive naturals, for example, 484 + ... + 525.

It is an arithmetic number, because the mean of its divisors is an integer number (4040).

2²¹¹⁸⁹ is an apocalyptic number.

It is an amenable number.

21189 is a deficient number, since it is larger than the sum of its proper divisors (11131).

21189 is a wasteful number, since it uses less digits than its factorization.

21189 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1019.

The product of its digits is 144, while the sum is 21.

The square root of 21189 is about 145.5644187293. The cubic root of 21189 is about 27.6717624200.

It can be divided in two parts, 211 and 89, that added together give a triangular number (300 = T₂₄).

The spelling of 21189 in words is "twenty-one thousand, one hundred eighty-nine".