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21360 has 40 divisors (see below), whose sum is σ = 66960. Its totient is φ = 5632.

The previous prime is 21347. The next prime is 21377. The reversal of 21360 is 6312.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (12).

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.

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, 196 + ... + 284.

It is an arithmetic number, because the mean of its divisors is an integer number (1674).

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).

21360 is an abundant number, since it is smaller than the sum of its proper divisors (45600).

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 sum of its prime factors is 105 (or 99 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 12.

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".