9999990 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a Curzon number.
It is a nialpdrome in base 10.
It is a congruent number.
Almost surely, 29999990 is an apocalyptic number.
9999990 is a gapful number since it is divisible by the number (90) formed by its first and last digit.
It is a practical number, because each smaller number is the sum of distinct divisors of 9999990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (18385920).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
9999990 is a wasteful number, since it uses less digits than its factorization.
9999990 is an evil number, because the sum of its binary digits is even.
The square root of 9999990 is about 3162.2760790292. The cubic root of 9999990 is about 215.4433971887.
The spelling of 9999990 in words is "nine million, nine hundred ninety-nine thousand, nine hundred ninety".