Let's divide 183601 by 21
The aim is to understand the frequency of 21 in 183601.

On to step 1:
The number 21 fits into 1 0 times, leaving 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.
Take the next digit (8) from the dividend and append it to 1, then repeat: 18 / 21

Step 2:
21 can be fit into 18 0 times, resulting in a remainder of 18.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 18 and we're left with 18.
Bring next digit (3) of the dividend behind the 18 and repeat the process: 183 / 21

Advancing to step 3:
21 goes into 183 8 times with a remainder of 15.
Record the quotient 8 as the next digit in the result. 
Result so far: 8.0
The remainder is 15 after subtracting 168 from 183.
Include the next digit (6) from the dividend after 15, then repeat: 156 / 21

Advancing to step 4:
21 goes into 156 7 times with a remainder of 9.
Record the quotient 7 as the next digit in the result. 
Result so far: 87.0
If we subtract 147 from 156, we get 9.
Include the next digit (0) from the dividend after 9, then repeat: 90 / 21

On to step 5:
If we divide 90 by 21, we get 4 and a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 874.0
If we take 84 away from 90, we end up with 6.
Fetch the next digit (1) from the dividend, attach it to 6 and continue: 61 / 21

Going ahead to step 6:
If we divide 61 by 21, we get 2 and a remainder of 19.
Put 2 as the next digit of the answer. 
Result so far: 8742.0
The remainder is 19 after subtracting 42 from 61.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 7:
21 goes into 190 9 times with a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 8742.9
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.

Step 8:
The number 21 fits into 10 0 times, leaving a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 8742.9
The remainder is 10 after subtracting 0 from 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 9:
When dividing 100 by 21, we get 4 with a remainder of 16.
The next digit of our result is 4. 
Result so far: 8742.904
If we subtract 84 from 100, 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.

Let's proceed to step 10:
If we divide 160 by 21, we get 7 and a remainder of 13.
Put 7 as the next digit of the answer. 
Result so far: 8742.9047
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 11:
21 goes into 130 6 times with a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 8742.90476
Subtract 126 from 130 to 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.

Going ahead to step 12:
40 divided by 21 is 1 with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 8742.904761
Subtract 21 from 40 to 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.

On to step 13:
21 can be fit into 190 9 times, resulting in a remainder of 1.
The next digit of our result is 9. 
Result so far: 8742.9047619
Subtracting 189 from 190 leaves us 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.

Advancing to step 14:
21 goes into 10 0 times with a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 8742.9047619
The remainder is 10 after subtracting 0 from 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Our division results in 8742.9047619 with a remaining 1e-08.