We look at the division of 15123663 by 861 
We're looking to find how many times 861 goes into 15123663.

Moving on to step 1:
If we divide 1 by 861, we get 0 and a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Append the next digit (5) from the dividend to 1 and continue with: 15 / 861

Let's proceed to step 2:
15 divided by 861 is 0 with a remainder of 15.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 15 to get 15.
Append the next digit (1) from the dividend to 15 and continue with: 151 / 861

Moving on to step 3:
When dividing 151 by 861, we get 0 with a remainder of 151.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 151, we get 151.
Fetch the next digit (2) from the dividend, attach it to 151 and continue: 1512 / 861

Moving on to step 4:
The number 861 fits into 1512 1 times, leaving a remainder of 651.
Write down 1 as next digit of the result. 
Result so far: 1.0
The remainder is 651 after subtracting 861 from 1512.
Fetch the next digit (3) from the dividend, attach it to 651 and continue: 6513 / 861

Going ahead to step 5:
If we divide 6513 by 861, we get 7 and a remainder of 486.
The next digit of our result is 7. 
Result so far: 17.0
Subtract 6027 from 6513 to get 486.
Append the next digit (6) from the dividend to 486 and continue with: 4866 / 861

Going ahead to step 6:
861 can be fit into 4866 5 times, resulting in a remainder of 561.
Put 5 as the next digit of the answer. 
Result so far: 175.0
Subtract 4305 from 4866 to get 561.
Bring next digit (6) of the dividend behind the 561 and repeat the process: 5616 / 861

On to step 7:
The number 861 fits into 5616 6 times, leaving a remainder of 450.
Record the quotient 6 as the next digit in the result. 
Result so far: 1756.0
If we subtract 5166 from 5616, we get 450.
Fetch the next digit (3) from the dividend, attach it to 450 and continue: 4503 / 861

Going ahead to step 8:
861 can be fit into 4503 5 times, resulting in a remainder of 198.
The next digit of our result is 5. 
Result so far: 17565.0
If we subtract 4305 from 4503, we get 198.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1980, and continue the process.

Moving on to step 9:
When dividing 1980 by 861, we get 2 with a remainder of 258.
The next digit of our result is 2. 
Result so far: 17565.2
Deduct 1722 from 1980 and we're left with 258.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2580, and continue the process.

Going ahead to step 10:
861 can be fit into 2580 2 times, resulting in a remainder of 858.
Use 2 as the next digit of our solution. 
Result so far: 17565.22
Deduct 1722 from 2580 and we're left with 858.
Since there are no more digits in the dividend, we add a zero to the remainder making it 8580, and continue the process.

After the division, we end up with 17565.22 and a remainder of 0.858.