6521 ÷ 6 = 1086 R5
No problem, we've got 6521 and 6 for the division.

Step 1:
6 goes into 6 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 6 from 6 to get 0.
Bring next digit (5) of the dividend behind the 0 and repeat the process: 5 / 6

Step 2:
6 goes into 5 0 times with a remainder of 5.
Write down 0 as next digit of of the result. 
Result so far: 10
Subtract 0 from 5 to get 5.
Bring next digit (2) of the dividend behind the 5 and repeat the process: 52 / 6

Step 3:
6 goes into 52 8 times with a remainder of 4.
Write down 8 as next digit of of the result. 
Result so far: 108
Subtract 48 from 52 to get 4.
Bring next digit (1) of the dividend behind the 4 and repeat the process: 41 / 6

Step 4:
6 goes into 41 6 times with a remainder of 5.
Write down 6 as next digit of of the result. 
Result so far: 1086
Subtract 36 from 41 to get 5.

The final result is 1086 with a remainder of 5.