If I have a house for $190,000, put a down payment of $18,000 and get a loan for $172,000 for 6.5% APR for 15 years, my monthly payment with simple interest would be $931.67.

I'm confused because I'm trying to figure out the TOTAL interest that I will pay to the bank. I am multiplying my monthly payment of $931.67 times 180 months (or 15 years) and getting $167,700.60 which is LESS than my original loan! Which means I wouldn't have paid any interest on the loan. Am I doing this correctly?

Thanks!