603859 ÷ 15 
We want to divide 603859 by 15.

Going ahead to step 1:
6 divided by 15 is 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Grab the next digit (0) from the dividend, add it to 6, then carry on: 60 / 15

Advancing to step 2:
15 can be fit into 60 4 times, resulting in a remainder of 0.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
The remainder is 0 after subtracting 60 from 60.
Grab the next digit (3) from the dividend, add it to 0, then carry on: 3 / 15

Step 3:
15 can be fit into 3 0 times, resulting in a remainder of 3.
Use 0 as the next digit of our solution. 
Result so far: 40.0
If we take 0 away from 3, we end up with 3.
Bring next digit (8) of the dividend behind the 3 and repeat the process: 38 / 15

Moving on to step 4:
When dividing 38 by 15, we get 2 with a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 402.0
If we subtract 30 from 38, we get 8.
Fetch the next digit (5) from the dividend, attach it to 8 and continue: 85 / 15

Advancing to step 5:
When dividing 85 by 15, we get 5 with a remainder of 10.
The next digit of our result is 5. 
Result so far: 4025.0
Subtracting 75 from 85 leaves us with 10.
Append the next digit (9) from the dividend to 10 and continue with: 109 / 15

Advancing to step 6:
15 goes into 109 7 times with a remainder of 4.
Use 7 as the next digit of our solution. 
Result so far: 40257.0
Subtracting 105 from 109 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Going ahead to step 7:
40 divided by 15 is 2 with a remainder of 10.
Record the quotient 2 as the next digit in the result. 
Result so far: 40257.2
Deduct 30 from 40 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 8:
15 goes into 100 6 times with a remainder of 10.
The number 6 becomes the next digit in our result. 
Result so far: 40257.26
Subtracting 90 from 100 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 9:
15 can be fit into 100 6 times, resulting in a remainder of 10.
Use 6 as the next digit of our solution. 
Result so far: 40257.266
If we subtract 90 from 100, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

After the division, we end up with 40257.266 and a remainder of 0.001.