863610 ÷ 21 
Let's see how many times 21 fits into 863610.

Moving on to step 1:
If we divide 8 by 21, we get 0 and a remainder of 8.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Take the next digit (6) from the dividend and append it to 8, then repeat: 86 / 21

On to step 2:
86 divided by 21 is 4 with a remainder of 2.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
Subtracting 84 from 86 leaves us with 2.
Bring next digit (3) of the dividend behind the 2 and repeat the process: 23 / 21

Advancing to step 3:
The number 21 fits into 23 1 times, leaving a remainder of 2.
The number 1 becomes the next digit in our result. 
Result so far: 41.0
Deduct 21 from 23 and we're left with 2.
Fetch the next digit (6) from the dividend, attach it to 2 and continue: 26 / 21

On to step 4:
When dividing 26 by 21, we get 1 with a remainder of 5.
Write down 1 as next digit of the result. 
Result so far: 411.0
Subtracting 21 from 26 leaves us with 5.
Bring next digit (1) of the dividend behind the 5 and repeat the process: 51 / 21

On to step 5:
21 goes into 51 2 times with a remainder of 9.
Write down 2 as next digit of the result. 
Result so far: 4112.0
If we take 42 away from 51, we end up with 9.
Grab the next digit (0) from the dividend, add it to 9, then carry on: 90 / 21

Going ahead to step 6:
If we divide 90 by 21, we get 4 and a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 41124.0
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Going ahead to step 7:
21 goes into 60 2 times with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 41124.2
If we subtract 42 from 60, we get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 8:
If we divide 180 by 21, we get 8 and a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 41124.28
If we subtract 168 from 180, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 9:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 41124.285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 10:
21 goes into 150 7 times with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 41124.2857
Deduct 147 from 150 and we're left with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 11:
30 divided by 21 is 1 with a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 41124.28571
If we subtract 21 from 30, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 12:
90 divided by 21 is 4 with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 41124.285714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 13:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 41124.2857142
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 14:
The number 21 fits into 180 8 times, leaving a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 41124.28571428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final result is 41124.28571428 with a remainder of 1.2e-08.