21240 ÷ 9 = 2360 R0
Alright, let's work through the division of 21240 by 9 step by step.

Step 1:
9 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 / 9

Step 2:
9 goes into 21 2 times with a remainder of 3.
Write down 2 as next digit of of the result. 
Result so far: 2
Subtract 18 from 21 to get 3.
Bring next digit (2) of the dividend behind the 3 and repeat the process: 32 / 9

Step 3:
9 goes into 32 3 times with a remainder of 5.
Write down 3 as next digit of of the result. 
Result so far: 23
Subtract 27 from 32 to get 5.
Bring next digit (4) of the dividend behind the 5 and repeat the process: 54 / 9

Step 4:
9 goes into 54 6 times with a remainder of 0.
Write down 6 as next digit of of the result. 
Result so far: 236
Subtract 54 from 54 to get 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 9

Step 5:
9 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of of the result. 
Result so far: 2360
Subtract 0 from 0 to get 0.

The final result is 2360 with a remainder of 0.