Let's divide 651338 by 21
The aim is to understand the frequency of 21 in 651338.

Step 1:
If we divide 6 by 21, we get 0 and 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.
Take the next digit (5) from the dividend and append it to 6, then repeat: 65 / 21

On to step 2:
The number 21 fits into 65 3 times, leaving a remainder of 2.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Deduct 63 from 65 and we're left with 2.
Fetch the next digit (1) from the dividend, attach it to 2 and continue: 21 / 21

Advancing to step 3:
21 can be fit into 21 1 times, resulting in a remainder of 0.
The next digit of our result is 1. 
Result so far: 31.0
If we subtract 21 from 21, we get 0.
Fetch the next digit (3) from the dividend, attach it to 0 and continue: 3 / 21

On to step 4:
21 goes into 3 0 times with a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 310.0
If we take 0 away from 3, we end up with 3.
Fetch the next digit (3) from the dividend, attach it to 3 and continue: 33 / 21

Advancing to step 5:
21 can be fit into 33 1 times, resulting in a remainder of 12.
The next digit of our result is 1. 
Result so far: 3101.0
The remainder is 12 after subtracting 21 from 33.
Include the next digit (8) from the dividend after 12, then repeat: 128 / 21

Going ahead to step 6:
21 goes into 128 6 times with a remainder of 2.
Write down 6 as next digit of the result. 
Result so far: 31016.0
The remainder is 2 after subtracting 126 from 128.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Going ahead to step 7:
If we divide 20 by 21, we get 0 and a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 31016.0
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.

On to step 8:
21 can be fit into 200 9 times, resulting in a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 31016.09
Deduct 189 from 200 and we're left with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Moving on to step 9:
110 divided by 21 is 5 with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 31016.095
If we take 105 away from 110, we end up with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Let's proceed to step 10:
50 divided by 21 is 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 31016.0952
Deduct 42 from 50 and we're left 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.

On to step 11:
21 can be fit into 80 3 times, resulting in a remainder of 17.
The next digit of our result is 3. 
Result so far: 31016.09523
If we subtract 63 from 80, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Moving on to step 12:
21 can be fit into 170 8 times, resulting in a remainder of 2.
Put 8 as the next digit of the answer. 
Result so far: 31016.095238
Subtract 168 from 170 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Going ahead to step 13:
21 goes into 20 0 times with a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 31016.095238
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 14:
200 divided by 21 is 9 with a remainder of 11.
The next digit of our result is 9. 
Result so far: 31016.09523809
Subtract 189 from 200 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.

Our division results in 31016.09523809 with a remaining 1.1e-08.