It is a tau number, because it is divible by the number of its divisors (40).
It is a nialpdrome in base 3 and base 10.
It is a congruent number.
It is an unprimeable number.
29840 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 9840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (15624).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
9840 is a wasteful number, since it uses less digits than its factorization.
9840 is an evil number, because the sum of its binary digits is even.
The square root of 9840 is about 99.1967741411. The cubic root of 9840 is about 21.4288253938.
The spelling of 9840 in words is "nine thousand, eight hundred forty".