It is a zygodrome in base 3.
It is an unprimeable number.
Almost surely, 221520800 is an apocalyptic number.
21520800 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 21520800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44862363).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21520800 is a wasteful number, since it uses less digits than its factorization.
21520800 is an evil number, because the sum of its binary digits is even.
The square root of 21520800 is about 4639.0516272186. The cubic root of 21520800 is about 278.1545299622.
The spelling of 21520800 in words is "twenty-one million, five hundred twenty thousand, eight hundred".