I'm sure this is probably in geek mathematics books and it's old news-- but I, not being a math major had never seen this before and found it facinating.

 

1 x 1	=	1
11 x 11	=	121
111 x 111	=	12321
1111 x 1111	=	1234321
11111 x 11111	=	123454321
111111 x 111111	=	12345654321
1111111 x 1111111	=	1234567654321
11111111 x 11111111	=	123456787654321
111111111 x 111111111	=	12345678987654321