c, q, and r are positive integers. If c, q, and r are assembled into the six-digit number cqrcqr, which one of the following must be a factor of cqrcqr?  Pick one:
A) 23
B) 19
C) 17
D) 7
E) none of the above
One short way -   cqrcqr = 1000cqr + cqr = (1000+1)= 
<gadget id="calculator">(1000+1)</gadget>
<output>1_001</output>
1001cqr   Therefore any factor of 1001 is a factor of cqrcqr   7 is a factor of 1001   So 7
<result>D</result>
c, q, and r are positive integers. If c, q, and r are assembled into the six-digit number cqrcqr, which one of the following must be a factor of cqrcqr?