Answer:
Step-by-step explanation:
We don't know if the number can start with a 0 or 1. Since we don't know, I will assume the number can start with either. The restriction is on 6s.
The way this is worded, I'm not sure if the digits can be repeated or not. It sounds like they can.
9 * 9 * 9 * 9 * 9 * 9 = 531441
If you are not allowed to repeat and no digit is a 6 then you get
9 *8 * 7 * 6 * 5*4 = 60480
