Numbers - General Questions

What is the smallest digit that can replace * so that 586*4 is divisible by 9?

7443 is divisible by which of the following?

What is the unit digit of 67⁶⁴⁷?

What is the smallest digit that can replace * so that 1*805 is divisible by 9?

What is the smallest digit that can replace * so that 48*71 is divisible by 9?