BIN (Bank Identification Number)
The six-digit number assigned by Visa and MasterCard to identify a member (Issuer or Acquirer) or processor for authorization. clearing or settlement processing. The Issuer assigns the six digits as the first six digits of the card number. The Acquirer assigns the six digits as the first six digits of the merchant number. Visa numbers always begins with a 4 and MasterCard numbers with a 5.