It is a congruent number.
It is an unprimeable number.
Almost surely, 221029872 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 21029872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21449520).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21029872 is a wasteful number, since it uses less digits than its factorization.
21029872 is an odious number, because the sum of its binary digits is odd.
The square root of 21029872 is about 4585.8338391180. The cubic root of 21029872 is about 276.0231724576.
The spelling of 21029872 in words is "twenty-one million, twenty-nine thousand, eight hundred seventy-two".