We look at the division of 644989 by 21 
We want to figure out the number of times 644989 can be divided by 21.

Step 1:
When dividing 6 by 21, we get 0 with a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Include the next digit (4) from the dividend after 6, then repeat: 64 / 21

Advancing to step 2:
When dividing 64 by 21, we get 3 with a remainder of 1.
The number 3 becomes the next digit in our result. 
Result so far: 3.0
The remainder is 1 after subtracting 63 from 64.
Include the next digit (4) from the dividend after 1, then repeat: 14 / 21

Moving on to step 3:
14 divided by 21 is 0 with a remainder of 14.
The number 0 becomes the next digit in our result. 
Result so far: 30.0
If we subtract 0 from 14, we get 14.
Fetch the next digit (9) from the dividend, attach it to 14 and continue: 149 / 21

Moving on to step 4:
If we divide 149 by 21, we get 7 and a remainder of 2.
Record the quotient 7 as the next digit in the result. 
Result so far: 307.0
If we subtract 147 from 149, we get 2.
Fetch the next digit (8) from the dividend, attach it to 2 and continue: 28 / 21

Advancing to step 5:
The number 21 fits into 28 1 times, leaving a remainder of 7.
The next digit of our result is 1. 
Result so far: 3071.0
Subtract 21 from 28 to get 7.
Include the next digit (9) from the dividend after 7, then repeat: 79 / 21

Step 6:
If we divide 79 by 21, we get 3 and a remainder of 16.
The next digit of our result is 3. 
Result so far: 30713.0
If we subtract 63 from 79, we get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Moving on to step 7:
21 can be fit into 160 7 times, resulting in a remainder of 13.
The next digit of our result is 7. 
Result so far: 30713.7
Subtract 147 from 160 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 8:
The number 21 fits into 130 6 times, leaving a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 30713.76
If we subtract 126 from 130, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 9:
The number 21 fits into 40 1 times, leaving a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 30713.761
If we subtract 21 from 40, we get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Going ahead to step 10:
If we divide 190 by 21, we get 9 and a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 30713.7619
If we take 189 away from 190, we end up with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

On to step 11:
10 divided by 21 is 0 with a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 30713.7619
Deduct 0 from 10 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.

Moving on to step 12:
100 divided by 21 is 4 with a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 30713.761904
Deduct 84 from 100 and we're left 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.

Step 13:
160 divided by 21 is 7 with a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 30713.7619047
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

On to step 14:
When dividing 130 by 21, we get 6 with a remainder of 4.
Write down 6 as next digit of the result. 
Result so far: 30713.76190476
The remainder is 4 after subtracting 126 from 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

After the division, we end up with 30713.76190476 and a remainder of 4e-09.