We're dividing 86391026 by 210 
We want to figure out the number of times 86391026 can be divided by 210.

Advancing to step 1:
210 goes into 8 0 times with a remainder of 8.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Include the next digit (6) from the dividend after 8, then repeat: 86 / 210

Step 2:
210 can be fit into 86 0 times, resulting in a remainder of 86.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 86, we get 86.
Include the next digit (3) from the dividend after 86, then repeat: 863 / 210

Moving on to step 3:
210 can be fit into 863 4 times, resulting in a remainder of 23.
Write down 4 as next digit of the result. 
Result so far: 4.0
If we take 840 away from 863, we end up with 23.
Bring next digit (9) of the dividend behind the 23 and repeat the process: 239 / 210

Let's proceed to step 4:
210 can be fit into 239 1 times, resulting in a remainder of 29.
The next digit of our result is 1. 
Result so far: 41.0
Subtracting 210 from 239 leaves us with 29.
Append the next digit (1) from the dividend to 29 and continue with: 291 / 210

On to step 5:
If we divide 291 by 210, we get 1 and a remainder of 81.
Write down 1 as next digit of the result. 
Result so far: 411.0
Subtract 210 from 291 to get 81.
Take the next digit (0) from the dividend and append it to 81, then repeat: 810 / 210

Going ahead to step 6:
210 can be fit into 810 3 times, resulting in a remainder of 180.
The number 3 becomes the next digit in our result. 
Result so far: 4113.0
If we take 630 away from 810, we end up with 180.
Fetch the next digit (2) from the dividend, attach it to 180 and continue: 1802 / 210

Step 7:
210 goes into 1802 8 times with a remainder of 122.
Use 8 as the next digit of our solution. 
Result so far: 41138.0
If we subtract 1680 from 1802, we get 122.
Bring next digit (6) of the dividend behind the 122 and repeat the process: 1226 / 210

Step 8:
210 goes into 1226 5 times with a remainder of 176.
The next digit of our result is 5. 
Result so far: 411385.0
If we subtract 1050 from 1226, we get 176.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1760, and continue the process.

Step 9:
1760 divided by 210 is 8 with a remainder of 80.
Record the quotient 8 as the next digit in the result. 
Result so far: 411385.8
Deduct 1680 from 1760 and we're left with 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

Moving on to step 10:
If we divide 800 by 210, we get 3 and a remainder of 170.
The number 3 becomes the next digit in our result. 
Result so far: 411385.83
If we take 630 away from 800, we end up with 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1700, and continue the process.

Step 11:
210 can be fit into 1700 8 times, resulting in a remainder of 20.
The next digit of our result is 8. 
Result so far: 411385.838
The remainder is 20 after subtracting 1680 from 1700.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Let's proceed to step 12:
The number 210 fits into 200 0 times, leaving a remainder of 200.
The number 0 becomes the next digit in our result. 
Result so far: 411385.838
The remainder is 200 after subtracting 0 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

Step 13:
When dividing 2000 by 210, we get 9 with a remainder of 110.
Record the quotient 9 as the next digit in the result. 
Result so far: 411385.83809
Subtracting 1890 from 2000 leaves us with 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1100, and continue the process.

Advancing to step 14:
1100 divided by 210 is 5 with a remainder of 50.
Use 5 as the next digit of our solution. 
Result so far: 411385.838095
The remainder is 50 after subtracting 1050 from 1100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Let's proceed to step 15:
210 can be fit into 500 2 times, resulting in a remainder of 80.
Put 2 as the next digit of the answer. 
Result so far: 411385.8380952
Deduct 420 from 500 and we're left with 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

Going ahead to step 16:
210 goes into 800 3 times with a remainder of 170.
Record the quotient 3 as the next digit in the result. 
Result so far: 411385.83809523
Subtract 630 from 800 to get 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1700, and continue the process.

The final outcome is 411385.83809523, with a leftover of 1.7e-07.