21330 has 32 divisors (see below), whose sum is σ = 57600. Its totient is φ = 5616.

The previous prime is 21323. The next prime is 21341. The reversal of 21330 is 3312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 231 + ... + 309.

It is an arithmetic number, because the mean of its divisors is an integer number (1800).

2²¹³³⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21330, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28800).

21330 is an abundant number, since it is smaller than the sum of its proper divisors (36270).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21330 is a wasteful number, since it uses less digits than its factorization.

21330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95 (or 89 counting only the distinct ones).

The product of its (nonzero) digits is 18, while the sum is 9.

The square root of 21330 is about 146.0479373357. The cubic root of 21330 is about 27.7330063961.

Subtracting from 21330 its product of nonzero digits (18), we obtain a palindrome (21312).

Adding to 21330 its reverse (3312), we get a palindrome (24642).

It can be divided in two parts, 213 and 30, that added together give a 5-th power (243 = 3⁵).

The spelling of 21330 in words is "twenty-one thousand, three hundred thirty".