Aaron Parecki

"37ab-cdefgh-ijklm

All Amex cards start with 37

ab is tied to the country of issuance/market

cd usually relates to the product in the AmEx portfolio

e is billing cycle

fghi is account number

j is the issue number

kl are position on the account, starting with 00 for the main (basic) card holder

m is the Luhn/mod 10 check digit"