43121 ÷ 8 = 5390 R1
Let's divide 43121 by 8.

Step 1:
8 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 (3) of the dividend behind the 4 and repeat the process: 43 / 8

Step 2:
8 goes into 43 5 times with a remainder of 3.
Write down 5 as next digit of of the result. 
Result so far: 5
Subtract 40 from 43 to get 3.
Bring next digit (1) of the dividend behind the 3 and repeat the process: 31 / 8

Step 3:
8 goes into 31 3 times with a remainder of 7.
Write down 3 as next digit of of the result. 
Result so far: 53
Subtract 24 from 31 to get 7.
Bring next digit (2) of the dividend behind the 7 and repeat the process: 72 / 8

Step 4:
8 goes into 72 9 times with a remainder of 0.
Write down 9 as next digit of of the result. 
Result so far: 539
Subtract 72 from 72 to get 0.
Bring next digit (1) of the dividend behind the 0 and repeat the process: 1 / 8

Step 5:
8 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 5390
Subtract 0 from 1 to get 1.

The final result is 5390 with a remainder of 1.