number 91 has an odd property. No matter what integer you place
in front of and behind it, the 91 is always a factor of the new
number. We can put that as 91 is a factor of x91x where x is any
digit 1 to 9.
Eg: 3913 = 43 x 91, 8918 = 98 x 91, etc.
It has to work with any pair of outside digits, as long as they're both the same.
there any other numbers less than 10,000 with this same property?