21168 has 60 divisors (see below), whose sum is σ = 70680. Its totient is φ = 6048.

The previous prime is 21163. The next prime is 21169. The reversal of 21168 is 86112.

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 a Harshad number since it is a multiple of its sum of digits (18).

It is a nude number because it is divisible by every one of its digits.

Its product of digits (96) is a multiple of the sum of its prime divisors (12).

It is a zygodrome in base 7.

It is a self number, because there is not a number n which added to its sum of digits gives 21168.

It is not an unprimeable number, because it can be changed into a prime (21163) by changing a digit.

21168 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3021 + ... + 3027.

It is an arithmetic number, because the mean of its divisors is an integer number (1178).

2²¹¹⁶⁸ is an apocalyptic number.

21168 is a gapful number since it is divisible by the number (28) 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 21168, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35340).

21168 is an abundant number, since it is smaller than the sum of its proper divisors (49512).

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

21168 is a wasteful number, since it uses less digits than its factorization.

21168 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31 (or 12 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

The square root of 21168 is about 145.4922678358. The cubic root of 21168 is about 27.6626177524.

21168 divided by its sum of digits (18) gives a triangular number (1176 = T₄₈).

The spelling of 21168 in words is "twenty-one thousand, one hundred sixty-eight".