It is a tau number, because it is divible by the number of its divisors (20).
It is a nialpdrome in base 10.
It is a zygodrome in base 2.
It is a congruent number.
It is an unprimeable number.
26640 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 6640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7812).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
6640 is a wasteful number, since it uses less digits than its factorization.
6640 is an odious number, because the sum of its binary digits is odd.
The square root of 6640 is about 81.4861951499. The cubic root of 6640 is about 18.7955927499.
The spelling of 6640 in words is "six thousand, six hundred forty".