644636 divided by 15 
We're looking to find how many times 15 goes into 644636.

Step 1:
The number 15 fits into 6 0 times, leaving a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Fetch the next digit (4) from the dividend, attach it to 6 and continue: 64 / 15

Step 2:
64 divided by 15 is 4 with a remainder of 4.
The number 4 becomes the next digit in our result. 
Result so far: 4.0
If we take 60 away from 64, we end up with 4.
Grab the next digit (4) from the dividend, add it to 4, then carry on: 44 / 15

Let's proceed to step 3:
15 goes into 44 2 times with a remainder of 14.
Use 2 as the next digit of our solution. 
Result so far: 42.0
If we take 30 away from 44, we end up with 14.
Include the next digit (6) from the dividend after 14, then repeat: 146 / 15

Step 4:
15 can be fit into 146 9 times, resulting in a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 429.0
If we subtract 135 from 146, we get 11.
Fetch the next digit (3) from the dividend, attach it to 11 and continue: 113 / 15

Step 5:
When dividing 113 by 15, we get 7 with a remainder of 8.
Write down 7 as next digit of the result. 
Result so far: 4297.0
The remainder is 8 after subtracting 105 from 113.
Fetch the next digit (6) from the dividend, attach it to 8 and continue: 86 / 15

Going ahead to step 6:
If we divide 86 by 15, we get 5 and a remainder of 11.
The number 5 becomes the next digit in our result. 
Result so far: 42975.0
Subtract 75 from 86 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Going ahead to step 7:
If we divide 110 by 15, we get 7 and a remainder of 5.
Use 7 as the next digit of our solution. 
Result so far: 42975.7
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 8:
The number 15 fits into 50 3 times, leaving a remainder of 5.
Use 3 as the next digit of our solution. 
Result so far: 42975.73
The remainder is 5 after subtracting 45 from 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 9:
When dividing 50 by 15, we get 3 with a remainder of 5.
Use 3 as the next digit of our solution. 
Result so far: 42975.733
Subtract 45 from 50 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

The quotient of the division is 42975.733, and the remainder is 0.0005.