640 ÷ 4 = 160 R0
Alright, let's work through the division of 640 by 4 step by step.

Step 1:
4 goes into 6 1 times with a remainder of 2.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 4 from 6 to get 2.
Bring next digit (4) of the dividend behind the 2 and repeat the process: 24 / 4

Step 2:
4 goes into 24 6 times with a remainder of 0.
Write down 6 as next digit of of the result. 
Result so far: 16
Subtract 24 from 24 to get 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 4

Step 3:
4 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of of the result. 
Result so far: 160
Subtract 0 from 0 to get 0.

The final result is 160 with a remainder of 0.