12960687 ÷ 644 
Let's see how many times 644 fits into 12960687.

Moving on to step 1:
1 divided by 644 is 0 with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 644

On to step 2:
12 divided by 644 is 0 with a remainder of 12.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 12, we end up with 12.
Include the next digit (9) from the dividend after 12, then repeat: 129 / 644

Moving on to step 3:
644 can be fit into 129 0 times, resulting in a remainder of 129.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 129 and we're left with 129.
Fetch the next digit (6) from the dividend, attach it to 129 and continue: 1296 / 644

Moving on to step 4:
1296 divided by 644 is 2 with a remainder of 8.
The next digit of our result is 2. 
Result so far: 2.0
The remainder is 8 after subtracting 1288 from 1296.
Bring next digit (0) of the dividend behind the 8 and repeat the process: 80 / 644

Let's proceed to step 5:
80 divided by 644 is 0 with a remainder of 80.
Put 0 as the next digit of the answer. 
Result so far: 20.0
Subtract 0 from 80 to get 80.
Grab the next digit (6) from the dividend, add it to 80, then carry on: 806 / 644

Moving on to step 6:
806 divided by 644 is 1 with a remainder of 162.
Record the quotient 1 as the next digit in the result. 
Result so far: 201.0
If we subtract 644 from 806, we get 162.
Append the next digit (8) from the dividend to 162 and continue with: 1628 / 644

Advancing to step 7:
When dividing 1628 by 644, we get 2 with a remainder of 340.
The next digit of our result is 2. 
Result so far: 2012.0
Subtracting 1288 from 1628 leaves us with 340.
Take the next digit (7) from the dividend and append it to 340, then repeat: 3407 / 644

Step 8:
644 goes into 3407 5 times with a remainder of 187.
The next digit of our result is 5. 
Result so far: 20125.0
If we subtract 3220 from 3407, we get 187.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1870, and continue the process.

Let's proceed to step 9:
1870 divided by 644 is 2 with a remainder of 582.
Use 2 as the next digit of our solution. 
Result so far: 20125.2
Subtract 1288 from 1870 to get 582.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5820, and continue the process.

Step 10:
If we divide 5820 by 644, we get 9 and a remainder of 24.
The next digit of our result is 9. 
Result so far: 20125.29
If we subtract 5796 from 5820, we get 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Let's proceed to step 11:
644 can be fit into 240 0 times, resulting in a remainder of 240.
Record the quotient 0 as the next digit in the result. 
Result so far: 20125.29
Subtract 0 from 240 to get 240.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2400, and continue the process.

Let's proceed to step 12:
The number 644 fits into 2400 3 times, leaving a remainder of 468.
The number 3 becomes the next digit in our result. 
Result so far: 20125.2903
Subtracting 1932 from 2400 leaves us with 468.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4680, and continue the process.

Advancing to step 13:
4680 divided by 644 is 7 with a remainder of 172.
The number 7 becomes the next digit in our result. 
Result so far: 20125.29037
The remainder is 172 after subtracting 4508 from 4680.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1720, and continue the process.

Going ahead to step 14:
When dividing 1720 by 644, we get 2 with a remainder of 432.
Put 2 as the next digit of the answer. 
Result so far: 20125.290372
If we take 1288 away from 1720, we end up with 432.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4320, and continue the process.

Step 15:
If we divide 4320 by 644, we get 6 and a remainder of 456.
Record the quotient 6 as the next digit in the result. 
Result so far: 20125.2903726
If we subtract 3864 from 4320, we get 456.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4560, and continue the process.

Step 16:
The number 644 fits into 4560 7 times, leaving a remainder of 52.
Record the quotient 7 as the next digit in the result. 
Result so far: 20125.29037267
Deduct 4508 from 4560 and we're left with 52.
Since there are no more digits in the dividend, we add a zero to the remainder making it 520, and continue the process.

The final outcome is 20125.29037267, with a leftover of 5.2e-08.