21600 has 72 divisors (see below), whose sum is σ = 78120. Its totient is φ = 5760.

The previous prime is 21599. The next prime is 21601. The reversal of 21600 is 612.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It is an interprime number because it is at equal distance from previous prime (21599) and next prime (21601).

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a nialpdrome in base 15.

It is a zygodrome in base 7 and base 15.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21600.

It is not an unprimeable number, because it can be changed into a prime (21601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4318 + ... + 4322.

It is an arithmetic number, because the mean of its divisors is an integer number (1085).

21600 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 21600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39060).

21600 is an abundant number, since it is smaller than the sum of its proper divisors (56520).

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

21600 is a wasteful number, since it uses less digits than its factorization.

21600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29 (or 10 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

The square root of 21600 is about 146.9693845670. The cubic root of 21600 is about 27.8495330017.

Adding to 21600 its product of nonzero digits (12), we get a palindrome (21612).

The spelling of 21600 in words is "twenty-one thousand, six hundred".