21537 ÷ 6 = 3589 R3
We're going to perform division on 21537 with 6 as the divisor.

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 (3) of the dividend behind the 5 and repeat the process: 53 / 6

Step 4:
6 goes into 53 8 times with a remainder of 5.
Write down 8 as next digit of of the result. 
Result so far: 358
Subtract 48 from 53 to get 5.
Bring next digit (7) of the dividend behind the 5 and repeat the process: 57 / 6

Step 5:
6 goes into 57 9 times with a remainder of 3.
Write down 9 as next digit of of the result. 
Result so far: 3589
Subtract 54 from 57 to get 3.

The final result is 3589 with a remainder of 3.