644843 divided by 28 
The aim is to understand the frequency of 28 in 644843.

Moving on to step 1:
When dividing 6 by 28, we get 0 with a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 6, we get 6.
Append the next digit (4) from the dividend to 6 and continue with: 64 / 28

On to step 2:
28 goes into 64 2 times with a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
Deduct 56 from 64 and we're left with 8.
Fetch the next digit (4) from the dividend, attach it to 8 and continue: 84 / 28

Moving on to step 3:
28 can be fit into 84 3 times, resulting in a remainder of 0.
The next digit of our result is 3. 
Result so far: 23.0
Deduct 84 from 84 and we're left with 0.
Append the next digit (8) from the dividend to 0 and continue with: 8 / 28

Moving on to step 4:
8 divided by 28 is 0 with a remainder of 8.
Put 0 as the next digit of the answer. 
Result so far: 230.0
Subtracting 0 from 8 leaves us with 8.
Grab the next digit (4) from the dividend, add it to 8, then carry on: 84 / 28

Step 5:
The number 28 fits into 84 3 times, leaving a remainder of 0.
Use 3 as the next digit of our solution. 
Result so far: 2303.0
Subtract 84 from 84 to get 0.
Append the next digit (3) from the dividend to 0 and continue with: 3 / 28

Moving on to step 6:
3 divided by 28 is 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 23030.0
The remainder is 3 after subtracting 0 from 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Going ahead to step 7:
The number 28 fits into 30 1 times, leaving a remainder of 2.
The number 1 becomes the next digit in our result. 
Result so far: 23030.1
Deduct 28 from 30 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 8:
When dividing 20 by 28, we get 0 with a remainder of 20.
The next digit of our result is 0. 
Result so far: 23030.1
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Moving on to step 9:
The number 28 fits into 200 7 times, leaving a remainder of 4.
Write down 7 as next digit of the result. 
Result so far: 23030.107
The remainder is 4 after subtracting 196 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 10:
28 can be fit into 40 1 times, resulting in a remainder of 12.
Write down 1 as next digit of the result. 
Result so far: 23030.1071
Deduct 28 from 40 and we're left 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.

On to step 11:
If we divide 120 by 28, we get 4 and a remainder of 8.
Record the quotient 4 as the next digit in the result. 
Result so far: 23030.10714
If we take 112 away from 120, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Advancing to step 12:
If we divide 80 by 28, we get 2 and a remainder of 24.
Use 2 as the next digit of our solution. 
Result so far: 23030.107142
Subtract 56 from 80 to 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.

Moving on to step 13:
When dividing 240 by 28, we get 8 with a remainder of 16.
Write down 8 as next digit of the result. 
Result so far: 23030.1071428
Deduct 224 from 240 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 14:
When dividing 160 by 28, we get 5 with a remainder of 20.
Record the quotient 5 as the next digit in the result. 
Result so far: 23030.10714285
Subtracting 140 from 160 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

After the division, we end up with 23030.10714285 and a remainder of 2e-08.