21888 has 48 divisors (see below), whose sum is σ = 66300. Its totient is φ = 6912.

The previous prime is 21881. The next prime is 21893. The reversal of 21888 is 88812.

It is a tau number, because it is divible by the number of its divisors (48).

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

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 21888.

It is not an unprimeable number, because it can be changed into a prime (21881) by changing a digit.

21888 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 (5) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1143 + ... + 1161.

2²¹⁸⁸⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33150).

21888 is an abundant number, since it is smaller than the sum of its proper divisors (44412).

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

21888 is a wasteful number, since it uses less digits than its factorization.

21888 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39 (or 24 counting only the distinct ones).

The product of its digits is 1024, while the sum is 27.

The square root of 21888 is about 147.9459360713. The cubic root of 21888 is about 27.9727626287.

It can be divided in two parts, 21 and 888, that added together give a palindrome (909).

The spelling of 21888 in words is "twenty-one thousand, eight hundred eighty-eight".