2748.67。 The monthly payment of 420,000 yuan in 20 years is related to lending institutions, loan interest rates and repayment methods. The benchmark interest rate of the central bank is 4.90% for commercial loans with a term of more than five years, 3.25% for provident fund loans with a term of more than five years and 5.25% for 20 years. The 20-year monthly loan of 420,000 yuan can be repaid in the form of equal principal and interest repayment, and the monthly loan is 2748.67 yuan.