21384 has 48 divisors (see below), whose sum is σ = 65520. Its totient is φ = 6480.

The previous prime is 21383. The next prime is 21391. The reversal of 21384 is 48312.

Added to its reverse (48312) it gives a square (69696 = 264²).

21384 = 10³ + 11³ + ... + 17³.

It is a happy number.

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.

It is one of the 548 Lynch-Bell numbers.

Its product of digits (192) is a multiple of the sum of its prime divisors (16).

It is not an unprimeable number, because it can be changed into a prime (21383) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1939 + ... + 1949.

It is an arithmetic number, because the mean of its divisors is an integer number (1365).

2²¹³⁸⁴ is an apocalyptic number.

21384 is a gapful number since it is divisible by the number (24) 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 21384, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32760).

21384 is an abundant number, since it is smaller than the sum of its proper divisors (44136).

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

21384 is a wasteful number, since it uses less digits than its factorization.

21384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32 (or 16 counting only the distinct ones).

The product of its digits is 192, while the sum is 18.

The square root of 21384 is about 146.2326912834. The cubic root of 21384 is about 27.7563900551.

Adding to 21384 its reverse (48312), we get a palindrome (69696).

The spelling of 21384 in words is "twenty-one thousand, three hundred eighty-four".