21520 ÷ 6 = 3586 R4
Let's divide 21520 by 6.

Step 1:
6 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 (1) of the dividend behind the 2 and repeat the process: 21 / 6

Step 2:
6 goes into 21 3 times with a remainder of 3.
Write down 3 as next digit of of the result. 
Result so far: 3
Subtract 18 from 21 to get 3.
Bring next digit (5) of the dividend behind the 3 and repeat the process: 35 / 6

Step 3:
6 goes into 35 5 times with a remainder of 5.
Write down 5 as next digit of of the result. 
Result so far: 35
Subtract 30 from 35 to get 5.
Bring next digit (2) of the dividend behind the 5 and repeat the process: 52 / 6

Step 4:
6 goes into 52 8 times with a remainder of 4.
Write down 8 as next digit of of the result. 
Result so far: 358
Subtract 48 from 52 to get 4.
Bring next digit (0) of the dividend behind the 4 and repeat the process: 40 / 6

Step 5:
6 goes into 40 6 times with a remainder of 4.
Write down 6 as next digit of of the result. 
Result so far: 3586
Subtract 36 from 40 to get 4.

The final result is 3586 with a remainder of 4.