21058 ÷ 6 = 3509 R4
Let's divide 21058 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 (0) of the dividend behind the 3 and repeat the process: 30 / 6

Step 3:
6 goes into 30 5 times with a remainder of 0.
Write down 5 as next digit of of the result. 
Result so far: 35
Subtract 30 from 30 to get 0.
Bring next digit (5) of the dividend behind the 0 and repeat the process: 5 / 6

Step 4:
6 goes into 5 0 times with a remainder of 5.
Write down 0 as next digit of of the result. 
Result so far: 350
Subtract 0 from 5 to get 5.
Bring next digit (8) of the dividend behind the 5 and repeat the process: 58 / 6

Step 5:
6 goes into 58 9 times with a remainder of 4.
Write down 9 as next digit of of the result. 
Result so far: 3509
Subtract 54 from 58 to get 4.

The final result is 3509 with a remainder of 4.