We still need to pay back 350 thousand yuan. Calculate a loan of 600,000 yuan, and how much money is needed after prepayment of 6,543,800 yuan. Assume that the total loan amount is P (principal), the repaid part is called repaid principal, the prepayment amount is E, and the remaining amount to be repaid is R. After prepayment, the formula of the remaining amount to be repaid is: R=P- repaid principal-E. This formula tells us that in order to calculate the remaining loan, the repaid part and prepayment part need to be subtracted from the original loan. Interest is not considered in this calculation. In the actual loan, prepayment will reduce the future interest payment, but for the sake of simplicity, this is not considered in the calculation here. After repaying 6,543,800 yuan in advance, it is still necessary to repay 350,000 yuan.