Let's divide 811915 by 21
The aim is to understand the frequency of 21 in 811915.

Advancing to step 1:
8 divided by 21 is 0 with a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 8 leaves us with 8.
Include the next digit (1) from the dividend after 8, then repeat: 81 / 21

Going ahead to step 2:
21 can be fit into 81 3 times, resulting in a remainder of 18.
Use 3 as the next digit of our solution. 
Result so far: 3.0
If we take 63 away from 81, we end up with 18.
Bring next digit (1) of the dividend behind the 18 and repeat the process: 181 / 21

Let's proceed to step 3:
181 divided by 21 is 8 with a remainder of 13.
Write down 8 as next digit of the result. 
Result so far: 38.0
The remainder is 13 after subtracting 168 from 181.
Take the next digit (9) from the dividend and append it to 13, then repeat: 139 / 21

Let's proceed to step 4:
If we divide 139 by 21, we get 6 and a remainder of 13.
Write down 6 as next digit of the result. 
Result so far: 386.0
If we take 126 away from 139, we end up with 13.
Include the next digit (1) from the dividend after 13, then repeat: 131 / 21

On to step 5:
When dividing 131 by 21, we get 6 with a remainder of 5.
Use 6 as the next digit of our solution. 
Result so far: 3866.0
Subtract 126 from 131 to get 5.
Fetch the next digit (5) from the dividend, attach it to 5 and continue: 55 / 21

Going ahead to step 6:
When dividing 55 by 21, we get 2 with a remainder of 13.
The next digit of our result is 2. 
Result so far: 38662.0
If we subtract 42 from 55, 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.

Going ahead to step 7:
130 divided by 21 is 6 with a remainder of 4.
Write down 6 as next digit of the result. 
Result so far: 38662.6
Deduct 126 from 130 and we're left with 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 8:
If we divide 40 by 21, we get 1 and a remainder of 19.
Write down 1 as next digit of the result. 
Result so far: 38662.61
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 9:
21 can be fit into 190 9 times, resulting in a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 38662.619
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Moving on to step 10:
21 goes into 10 0 times with a remainder of 10.
Write down 0 as next digit of the result. 
Result so far: 38662.619
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.

Advancing to step 11:
The number 21 fits into 100 4 times, leaving a remainder of 16.
The next digit of our result is 4. 
Result so far: 38662.61904
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.

Let's proceed to step 12:
If we divide 160 by 21, we get 7 and a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 38662.619047
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 13:
The number 21 fits into 130 6 times, leaving a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 38662.6190476
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.

Going ahead to step 14:
21 can be fit into 40 1 times, resulting in a remainder of 19.
Record the quotient 1 as the next digit in the result. 
Result so far: 38662.61904761
Subtracting 21 from 40 leaves us with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

In conclusion, the division gives 38662.61904761 with a balance of 1.9e-08.