We look at the division of 643641 by 86 
We want to divide 643641 by 86.

Advancing to step 1:
The number 86 fits into 6 0 times, leaving a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Append the next digit (4) from the dividend to 6 and continue with: 64 / 86

Advancing to step 2:
64 divided by 86 is 0 with a remainder of 64.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 64 to get 64.
Take the next digit (3) from the dividend and append it to 64, then repeat: 643 / 86

Step 3:
The number 86 fits into 643 7 times, leaving a remainder of 41.
The number 7 becomes the next digit in our result. 
Result so far: 7.0
If we subtract 602 from 643, we get 41.
Bring next digit (6) of the dividend behind the 41 and repeat the process: 416 / 86

On to step 4:
The number 86 fits into 416 4 times, leaving a remainder of 72.
The number 4 becomes the next digit in our result. 
Result so far: 74.0
The remainder is 72 after subtracting 344 from 416.
Bring next digit (4) of the dividend behind the 72 and repeat the process: 724 / 86

Step 5:
86 goes into 724 8 times with a remainder of 36.
Put 8 as the next digit of the answer. 
Result so far: 748.0
If we take 688 away from 724, we end up with 36.
Include the next digit (1) from the dividend after 36, then repeat: 361 / 86

Moving on to step 6:
361 divided by 86 is 4 with a remainder of 17.
Put 4 as the next digit of the answer. 
Result so far: 7484.0
Subtracting 344 from 361 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Going ahead to step 7:
The number 86 fits into 170 1 times, leaving a remainder of 84.
Use 1 as the next digit of our solution. 
Result so far: 7484.1
Subtract 86 from 170 to get 84.
Since there are no more digits in the dividend, we add a zero to the remainder making it 840, and continue the process.

Step 8:
86 goes into 840 9 times with a remainder of 66.
The number 9 becomes the next digit in our result. 
Result so far: 7484.19
The remainder is 66 after subtracting 774 from 840.
Since there are no more digits in the dividend, we add a zero to the remainder making it 660, and continue the process.

Moving on to step 9:
When dividing 660 by 86, we get 7 with a remainder of 58.
Put 7 as the next digit of the answer. 
Result so far: 7484.197
The remainder is 58 after subtracting 602 from 660.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

Going ahead to step 10:
580 divided by 86 is 6 with a remainder of 64.
Use 6 as the next digit of our solution. 
Result so far: 7484.1976
Subtracting 516 from 580 leaves us with 64.
Since there are no more digits in the dividend, we add a zero to the remainder making it 640, and continue the process.

Going ahead to step 11:
If we divide 640 by 86, we get 7 and a remainder of 38.
Put 7 as the next digit of the answer. 
Result so far: 7484.19767
If we take 602 away from 640, we end up with 38.
Since there are no more digits in the dividend, we add a zero to the remainder making it 380, and continue the process.

On to step 12:
When dividing 380 by 86, we get 4 with a remainder of 36.
Write down 4 as next digit of the result. 
Result so far: 7484.197674
Subtract 344 from 380 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Let's proceed to step 13:
360 divided by 86 is 4 with a remainder of 16.
The number 4 becomes the next digit in our result. 
Result so far: 7484.1976744
Deduct 344 from 360 and we're left with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

The final outcome is 7484.1976744, with a leftover of 1.6e-07.