chair number 
Let $Z$ be a $6$-digit positive integer, such as $247247$, whose first three digits are the same as its last three digits taken in the same order. Which of the following numbers must also be a factor of $Z$? (adapted from 2017 AMC 8 Problem, Question \#$7$) 
A. $$2$$ 
B. $$20$$ 
C. $$1001$$ 
D. $$111$$ 
E. $$1111$$ 