It is a tau number, because it is divible by the number of its divisors (80).
It is a nialpdrome in base 10.
It is a zygodrome in base 2.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 99840.
It is an unprimeable number.
299840 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 99840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (171864).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
99840 is a wasteful number, since it uses less digits than its factorization.
99840 is an evil number, because the sum of its binary digits is even.
The square root of 99840 is about 315.9746825301. The cubic root of 99840 is about 46.3911199812.
The spelling of 99840 in words is "ninety-nine thousand, eight hundred forty".