<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Centurion:
Since I started this thread I will go first 
The second to last digit of your card number tells you if your card is a primary card or secondary card of the account starting with zero for the primary card. Example:
3737 xxxxx 61003 is a primary card
3737 xxxxx 61013 is a secondary card
If I remember correctly your billing cycle could be determined in the past by your card # on US cards. Is this still true?
[This message has been edited by Centurion (edited 10-16-2003).]</font>
CLARIFICATION:
1. The primary card holder in the united states is the person responsible for the charges and opened and qualified for the account and whose name appears first on the statement. A secondary card holder can be several people who the primary card holder has a issued a card for spending on their account. You can have mored than one secondary card holder such as wife, children, friends. If you are a primary card holder and you lose your card the second card you recieve is still the primary account number even though you have another card and it may the second, third, etc. Also from the replies on this thread sugest the second to last digit rule seems to apply to US cards only