21879 ÷ 9 = 2431 R0
Alright, let's work through the division of 21879 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 (8) of the dividend behind the 3 and repeat the process: 38 / 9

Step 3:
9 goes into 38 4 times with a remainder of 2.
Write down 4 as next digit of of the result. 
Result so far: 24
Subtract 36 from 38 to get 2.
Bring next digit (7) of the dividend behind the 2 and repeat the process: 27 / 9

Step 4:
9 goes into 27 3 times with a remainder of 0.
Write down 3 as next digit of of the result. 
Result so far: 243
Subtract 27 from 27 to get 0.
Bring next digit (9) of the dividend behind the 0 and repeat the process: 9 / 9

Step 5:
9 goes into 9 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 2431
Subtract 9 from 9 to get 0.

The final result is 2431 with a remainder of 0.