80421 ÷ 6 = 13403 R3
No problem, we've got 80421 and 6 for the division.

Step 1:
6 goes into 8 1 times with a remainder of 2.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 6 from 8 to get 2.
Bring next digit (0) of the dividend behind the 2 and repeat the process: 20 / 6

Step 2:
6 goes into 20 3 times with a remainder of 2.
Write down 3 as next digit of of the result. 
Result so far: 13
Subtract 18 from 20 to get 2.
Bring next digit (4) of the dividend behind the 2 and repeat the process: 24 / 6

Step 3:
6 goes into 24 4 times with a remainder of 0.
Write down 4 as next digit of of the result. 
Result so far: 134
Subtract 24 from 24 to get 0.
Bring next digit (2) of the dividend behind the 0 and repeat the process: 2 / 6

Step 4:
6 goes into 2 0 times with a remainder of 2.
Write down 0 as next digit of of the result. 
Result so far: 1340
Subtract 0 from 2 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 6

Step 5:
6 goes into 21 3 times with a remainder of 3.
Write down 3 as next digit of of the result. 
Result so far: 13403
Subtract 18 from 21 to get 3.

The final result is 13403 with a remainder of 3.