21288320 has 128 divisors (see below), whose sum is σ = 55814400. Its totient is φ = 7741440.

The previous prime is 21288259. The next prime is 21288343. The reversal of 21288320 is 2388212.

It is a tau number, because it is divible by the number of its divisors (128).

It is a self number, because there is not a number n which added to its sum of digits gives 21288320.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 575342 + ... + 575378.

It is an arithmetic number, because the mean of its divisors is an integer number (436050).

Almost surely, 2^21288320 is an apocalyptic number.

21288320 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 21288320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27907200).

21288320 is an abundant number, since it is smaller than the sum of its proper divisors (34526080).

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

21288320 is a wasteful number, since it uses less digits than its factorization.

21288320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116 (or 104 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 26.

The square root of 21288320 is about 4613.9267441085. The cubic root of 21288320 is about 277.1493067445.

The spelling of 21288320 in words is "twenty-one million, two hundred eighty-eight thousand, three hundred twenty".