Based on the information provided, the following conclusions can be drawn:

1. The monthly repayment amount is 3500 yuan.

2. No loan period is provided, assuming the loan period is 12 months (i.e. one year).

3. The loan amount is 6,543,800+0.7 million.

According to the above conditions, calculate the total interest:

Total interest = 3,500 yuan/month × 12 months-170,000 yuan = 42,000 yuan.

Therefore, the loan needs to repay interest totaling 42,000 yuan.

Extended data:

Rural credit cooperatives are financial institutions in rural areas of China, providing various financial services for rural residents, including deposits, loans and other financial services. Loan is one of the common services of rural credit cooperatives, which can be used for personal consumption, agricultural production and rural housing construction. Loan interest is generally calculated and determined according to the loan amount, repayment period, interest rate and other factors. The monthly repayment amount depends on the loan amount and repayment period, while the total interest is determined by the loan amount and repayment period.