20161 ÷ 3 = 6720 R1
Let's divide 20161 by 3.

Step 1:
3 goes into 2 0 times with a remainder of 2.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 2 to get 2.
Bring next digit (0) of the dividend behind the 2 and repeat the process: 20 / 3

Step 2:
3 goes into 20 6 times with a remainder of 2.
Write down 6 as next digit of of the result. 
Result so far: 6
Subtract 18 from 20 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 3

Step 3:
3 goes into 21 7 times with a remainder of 0.
Write down 7 as next digit of of the result. 
Result so far: 67
Subtract 21 from 21 to get 0.
Bring next digit (6) of the dividend behind the 0 and repeat the process: 6 / 3

Step 4:
3 goes into 6 2 times with a remainder of 0.
Write down 2 as next digit of of the result. 
Result so far: 672
Subtract 6 from 6 to get 0.
Bring next digit (1) of the dividend behind the 0 and repeat the process: 1 / 3

Step 5:
3 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 6720
Subtract 0 from 1 to get 1.

The final result is 6720 with a remainder of 1.