It is a congruent number.
It is an unprimeable number.
Almost surely, 221589872 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 21589872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28180488).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21589872 is a wasteful number, since it uses less digits than its factorization.
21589872 is an odious number, because the sum of its binary digits is odd.
The square root of 21589872 is about 4646.4902883790. The cubic root of 21589872 is about 278.4517954231.
The spelling of 21589872 in words is "twenty-one million, five hundred eighty-nine thousand, eight hundred seventy-two".