There are 3 types of Personal Identification Numbers (PINs) that a Citibank customer gets- APIN, ATM Personal Identification Number, this PIN will be required at ATMs, POS or for certain online transactions. IPIN, Internet Personal Identification Number, this enables users to login into the Citibank online/mobile banking portal TPIN, Telephone Personal Identification Number, It is required when customer wishes to transact using the 24 Hour Citibank Service /ul