639871 divided by 45 
Our goal is to divide 639871 by 45.

On to step 1:
6 divided by 45 is 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Bring next digit (3) of the dividend behind the 6 and repeat the process: 63 / 45

Step 2:
The number 45 fits into 63 1 times, leaving a remainder of 18.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
The remainder is 18 after subtracting 45 from 63.
Grab the next digit (9) from the dividend, add it to 18, then carry on: 189 / 45

Advancing to step 3:
When dividing 189 by 45, we get 4 with a remainder of 9.
Use 4 as the next digit of our solution. 
Result so far: 14.0
The remainder is 9 after subtracting 180 from 189.
Bring next digit (8) of the dividend behind the 9 and repeat the process: 98 / 45

Advancing to step 4:
98 divided by 45 is 2 with a remainder of 8.
The next digit of our result is 2. 
Result so far: 142.0
If we subtract 90 from 98, we get 8.
Take the next digit (7) from the dividend and append it to 8, then repeat: 87 / 45

On to step 5:
45 goes into 87 1 times with a remainder of 42.
Write down 1 as next digit of the result. 
Result so far: 1421.0
If we take 45 away from 87, we end up with 42.
Fetch the next digit (1) from the dividend, attach it to 42 and continue: 421 / 45

Advancing to step 6:
If we divide 421 by 45, we get 9 and a remainder of 16.
Use 9 as the next digit of our solution. 
Result so far: 14219.0
If we take 405 away from 421, we end up with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Let's proceed to step 7:
When dividing 160 by 45, we get 3 with a remainder of 25.
Put 3 as the next digit of the answer. 
Result so far: 14219.3
The remainder is 25 after subtracting 135 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

Let's proceed to step 8:
45 goes into 250 5 times with a remainder of 25.
Write down 5 as next digit of the result. 
Result so far: 14219.35
If we take 225 away from 250, we end up with 25.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

On to step 9:
The number 45 fits into 250 5 times, leaving a remainder of 25.
Put 5 as the next digit of the answer. 
Result so far: 14219.355
If we subtract 225 from 250, we get 25.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

The final outcome is 14219.355, with a leftover of 0.0025.