It is a happy number.
7840 is nontrivially palindromic in base 3.
7840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
7840 is a gapful number since it is divisible by the number (70) formed by its first and last digit.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 7840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10773).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
7840 is a wasteful number, since it uses less digits than its factorization.
7840 is an evil number, because the sum of its binary digits is even.
The square root of 7840 is about 88.5437744847. The cubic root of 7840 is about 19.8657677676.
The spelling of 7840 in words is "seven thousand, eight hundred forty".