40421 ÷ 9 = 4491 R2
Alright, let's work through the division of 40421 by 9 step by step.

Step 1:
9 goes into 4 0 times with a remainder of 4.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 4 to get 4.
Bring next digit (0) of the dividend behind the 4 and repeat the process: 40 / 9

Step 2:
9 goes into 40 4 times with a remainder of 4.
Write down 4 as next digit of of the result. 
Result so far: 4
Subtract 36 from 40 to get 4.
Bring next digit (4) of the dividend behind the 4 and repeat the process: 44 / 9

Step 3:
9 goes into 44 4 times with a remainder of 8.
Write down 4 as next digit of of the result. 
Result so far: 44
Subtract 36 from 44 to get 8.
Bring next digit (2) of the dividend behind the 8 and repeat the process: 82 / 9

Step 4:
9 goes into 82 9 times with a remainder of 1.
Write down 9 as next digit of of the result. 
Result so far: 449
Subtract 81 from 82 to get 1.
Bring next digit (1) of the dividend behind the 1 and repeat the process: 11 / 9

Step 5:
9 goes into 11 1 times with a remainder of 2.
Write down 1 as next digit of of the result. 
Result so far: 4491
Subtract 9 from 11 to get 2.

The final result is 4491 with a remainder of 2.