We look at the division of 465845 by 21 
The aim is to understand the frequency of 21 in 465845.

On to step 1:
If we divide 4 by 21, we get 0 and a remainder of 4.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 4 after subtracting 0 from 4.
Fetch the next digit (6) from the dividend, attach it to 4 and continue: 46 / 21

Advancing to step 2:
The number 21 fits into 46 2 times, leaving a remainder of 4.
The next digit of our result is 2. 
Result so far: 2.0
If we take 42 away from 46, we end up with 4.
Include the next digit (5) from the dividend after 4, then repeat: 45 / 21

On to step 3:
21 goes into 45 2 times with a remainder of 3.
Record the quotient 2 as the next digit in the result. 
Result so far: 22.0
Subtracting 42 from 45 leaves us with 3.
Grab the next digit (8) from the dividend, add it to 3, then carry on: 38 / 21

On to step 4:
21 goes into 38 1 times with a remainder of 17.
Put 1 as the next digit of the answer. 
Result so far: 221.0
Subtracting 21 from 38 leaves us with 17.
Take the next digit (4) from the dividend and append it to 17, then repeat: 174 / 21

Step 5:
21 goes into 174 8 times with a remainder of 6.
The number 8 becomes the next digit in our result. 
Result so far: 2218.0
Subtract 168 from 174 to get 6.
Bring next digit (5) of the dividend behind the 6 and repeat the process: 65 / 21

Let's proceed to step 6:
21 goes into 65 3 times with a remainder of 2.
Put 3 as the next digit of the answer. 
Result so far: 22183.0
If we take 63 away from 65, we end up 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.

Let's proceed to step 7:
If we divide 20 by 21, we get 0 and a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 22183.0
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.

Advancing to step 8:
The number 21 fits into 200 9 times, leaving a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 22183.09
If we take 189 away from 200, we end up 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.

On to step 9:
When dividing 110 by 21, we get 5 with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 22183.095
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.

Step 10:
21 can be fit into 50 2 times, resulting in a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 22183.0952
If we subtract 42 from 50, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 11:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 22183.09523
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

On to step 12:
170 divided by 21 is 8 with a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 22183.095238
If we take 168 away from 170, we end up 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.

On to step 13:
21 can be fit into 20 0 times, resulting in a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 22183.095238
Subtracting 0 from 20 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.

On to step 14:
If we divide 200 by 21, we get 9 and a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 22183.09523809
Subtracting 189 from 200 leaves us 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.

Our division results in 22183.09523809 with a remaining 1.1e-08.