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 \#$7$) 
选项为:A:$$2$$  B:$$20$$  C:$$1001$$  D:$$111$$  E:$$1111$$  请回答其中一个选项.