It is a happy number.
9991920 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.
It is a congruent number.
It is an unprimeable number.
Almost surely, 29991920 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 9991920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (17141760).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
9991920 is a wasteful number, since it uses less digits than its factorization.
9991920 is an evil number, because the sum of its binary digits is even.
The square root of 9991920 is about 3160.9998418222. Note that the first 3 decimals coincide. The cubic root of 9991920 is about 215.3854272602.
The spelling of 9991920 in words is "nine million, nine hundred ninety-one thousand, nine hundred twenty".