Unified Payments Interface (UPI) is a real time payment system that is used for transferring money from one bank account to another using mobile platforms. 

There is no such thing as UPI number. But there are UPI Pin which can be set by the user to ensure safe transactions. UPI Pin is usually a 4-digit number that needs to be entered before initiating the transaction. The transaction will not happen if the number is wrongly entered. 

Also, there is UPI ID or Virtual Payment Address mapped against your bank account. Using the UPI ID, the users can send money from one account to another. 

UPI transactions can also be conducted using mobile number, Aadhaar Number and QR code.