A) 21 Explanation: According to NPCI, the UPI application of 19 banks can be downloaded from Google Play Store in next two to three working days. The list of banks providing the app on Google Play Store are: Andhra Bank, Axis Bank, Bank of Maharashtra, Bhartiya Mahila Bank, Canara Bank, Catholic Syrian Bank, DCB Bank, Federal Bank, ICICI Bank, TJSB Sahakari Bank, Oriental Bank of Commerce, Karnataka Bank, UCO Bank, Union Bank of India, United Bank of India, Punjab National Bank, South Indian Ban k The customers of IDBI Bank and RBL Bank can download any UPI enabled apps and link their account.