It is a tau number, because it is divible by the number of its divisors (40).
It is a nialpdrome in base 13.
It is a congruent number.
It is an unprimeable number.
21360 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
221360 is an apocalyptic number.
21360 is a gapful number since it is divisible by the number (20) formed by its first and last digit.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 21360, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33480).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21360 is a wasteful number, since it uses less digits than its factorization.
21360 is an odious number, because the sum of its binary digits is odd.
The square root of 21360 is about 146.1506072516. The cubic root of 21360 is about 27.7460021836.
Adding to 21360 its reverse (6312), we get a palindrome (27672).
The spelling of 21360 in words is "twenty-one thousand, three hundred sixty".