Start by looking at the back of your gift card. The first six digits for each credit card number are the bank id number, the same number for each card issued by that credit card. Last 4 digits of the primary accountholder's social security number.
(www.younkers.com) other store credit cards:
You can enter the card number either in 4 digit groups or without any spaces. However, you probably don’t have a social security number, which all credit card applications ask for. 4111 1111 4555 1142 security code optional: Show activity on this post.