It probably means it's an easy number to remember and that if it's possible to sell legally it could be worth a significant amount.
Since you asked a Rabbi about the number six, I should add that the number six is very significant in Judaism. It represents pure physicality in the world without any spirituality. There are six primary sides that "box" a person into this physical world. The Maharal of Prague (one of the greatest Jewish philosophers) says that the number 7 is the number 6 with an additional dimension of spirituality. In a box there are 6 sides but the seventh dimension is the the center, which is not physical but draws all the physical parts together and turns the mundane into something holy.