15599355 ÷ 858 
We want to figure out the number of times 15599355 can be divided by 858.

On to step 1:
858 can be fit into 1 0 times, resulting in a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Append the next digit (5) from the dividend to 1 and continue with: 15 / 858

On to step 2:
858 can be fit into 15 0 times, resulting in a remainder of 15.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 15 and we're left with 15.
Take the next digit (5) from the dividend and append it to 15, then repeat: 155 / 858

Going ahead to step 3:
858 goes into 155 0 times with a remainder of 155.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 155 and we're left with 155.
Include the next digit (9) from the dividend after 155, then repeat: 1559 / 858

On to step 4:
1559 divided by 858 is 1 with a remainder of 701.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Subtracting 858 from 1559 leaves us with 701.
Include the next digit (9) from the dividend after 701, then repeat: 7019 / 858

Moving on to step 5:
858 goes into 7019 8 times with a remainder of 155.
The next digit of our result is 8. 
Result so far: 18.0
Subtracting 6864 from 7019 leaves us with 155.
Take the next digit (3) from the dividend and append it to 155, then repeat: 1553 / 858

Advancing to step 6:
1553 divided by 858 is 1 with a remainder of 695.
Record the quotient 1 as the next digit in the result. 
Result so far: 181.0
Subtract 858 from 1553 to get 695.
Grab the next digit (5) from the dividend, add it to 695, then carry on: 6955 / 858

Moving on to step 7:
If we divide 6955 by 858, we get 8 and a remainder of 91.
Use 8 as the next digit of our solution. 
Result so far: 1818.0
Subtracting 6864 from 6955 leaves us with 91.
Append the next digit (5) from the dividend to 91 and continue with: 915 / 858

Going ahead to step 8:
When dividing 915 by 858, we get 1 with a remainder of 57.
Use 1 as the next digit of our solution. 
Result so far: 18181.0
Subtract 858 from 915 to get 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

On to step 9:
The number 858 fits into 570 0 times, leaving a remainder of 570.
Write down 0 as next digit of the result. 
Result so far: 18181.0
If we take 0 away from 570, we end up with 570.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5700, and continue the process.

Let's proceed to step 10:
5700 divided by 858 is 6 with a remainder of 552.
Record the quotient 6 as the next digit in the result. 
Result so far: 18181.06
If we subtract 5148 from 5700, we get 552.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5520, and continue the process.

On to step 11:
858 can be fit into 5520 6 times, resulting in a remainder of 372.
Record the quotient 6 as the next digit in the result. 
Result so far: 18181.066
The remainder is 372 after subtracting 5148 from 5520.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3720, and continue the process.

The quotient of the division is 18181.066, and the remainder is 0.0372.