9966 is an esthetic number in base 4, because in such base its adjacent digits differ by 1.
9966 is a strobogrammatic number because it is the same when read upside-down.
It is a plaindrome in base 8, base 14 and base 16.
It is a nialpdrome in base 10 and base 11.
It is a zygodrome in base 10.
It is a congruent number.
9966 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
29966 is an apocalyptic number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
9966 is a wasteful number, since it uses less digits than its factorization.
9966 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 167.
The square root of 9966 is about 99.8298552538. The cubic root of 9966 is about 21.5199022489.
The spelling of 9966 in words is "nine thousand, nine hundred sixty-six".