639987 ÷ 15 
We want to figure out the number of times 639987 can be divided by 15.

Let's proceed to step 1:
The number 15 fits into 6 0 times, leaving a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 6, we get 6.
Append the next digit (3) from the dividend to 6 and continue with: 63 / 15

Going ahead to step 2:
63 divided by 15 is 4 with a remainder of 3.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
Subtract 60 from 63 to get 3.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 15

Step 3:
15 goes into 39 2 times with a remainder of 9.
Write down 2 as next digit of the result. 
Result so far: 42.0
Subtract 30 from 39 to get 9.
Bring next digit (9) of the dividend behind the 9 and repeat the process: 99 / 15

Advancing to step 4:
15 goes into 99 6 times with a remainder of 9.
Record the quotient 6 as the next digit in the result. 
Result so far: 426.0
Subtract 90 from 99 to get 9.
Fetch the next digit (8) from the dividend, attach it to 9 and continue: 98 / 15

Moving on to step 5:
15 can be fit into 98 6 times, resulting in a remainder of 8.
The number 6 becomes the next digit in our result. 
Result so far: 4266.0
Deduct 90 from 98 and we're left with 8.
Append the next digit (7) from the dividend to 8 and continue with: 87 / 15

Let's proceed to step 6:
If we divide 87 by 15, we get 5 and a remainder of 12.
Use 5 as the next digit of our solution. 
Result so far: 42665.0
Subtracting 75 from 87 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 7:
When dividing 120 by 15, we get 8 with a remainder of 0.
Record the quotient 8 as the next digit in the result. 
Result so far: 42665.8
Subtracting 120 from 120 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 8:
0 divided by 15 is 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 42665.8
Subtract 0 from 0 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Moving on to step 9:
15 goes into 0 0 times with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 42665.8
Subtract 0 from 0 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 42665.8, with a leftover of 0.0.