Sure you can do it; it just might not feel so good.

My initial thought is that you would be better off--if your schedule allows--doing another long ride on Sunday and to take your rest day, instead, during the week. In the absence of being able to ride more during the week, adapting your body to do back-to-back long rides over may be the next best thing. If you can, try to fit in at least one ride in the 70-75 mile range before the event, too. How many miles are you currently doing each week? What kind of century is it (flat, rolling or mountain)? If there's any kind of climbing, you will need to specifically train for that too.