810265 divided by 21 
The aim is to understand the frequency of 21 in 810265.

Moving on to step 1:
21 goes into 8 0 times with a remainder of 8.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Bring next digit (1) of the dividend behind the 8 and repeat the process: 81 / 21

Going ahead to step 2:
If we divide 81 by 21, we get 3 and a remainder of 18.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Subtract 63 from 81 to get 18.
Append the next digit (0) from the dividend to 18 and continue with: 180 / 21

Going ahead to step 3:
21 can be fit into 180 8 times, resulting in a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 38.0
Deduct 168 from 180 and we're left with 12.
Take the next digit (2) from the dividend and append it to 12, then repeat: 122 / 21

Going ahead to step 4:
If we divide 122 by 21, we get 5 and a remainder of 17.
Record the quotient 5 as the next digit in the result. 
Result so far: 385.0
If we take 105 away from 122, we end up with 17.
Include the next digit (6) from the dividend after 17, then repeat: 176 / 21

Let's proceed to step 5:
The number 21 fits into 176 8 times, leaving a remainder of 8.
Put 8 as the next digit of the answer. 
Result so far: 3858.0
Deduct 168 from 176 and we're left with 8.
Append the next digit (5) from the dividend to 8 and continue with: 85 / 21

Let's proceed to step 6:
The number 21 fits into 85 4 times, leaving a remainder of 1.
The next digit of our result is 4. 
Result so far: 38584.0
Subtracting 84 from 85 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.

Let's proceed to step 7:
10 divided by 21 is 0 with a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 38584.0
Subtract 0 from 10 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 8:
21 can be fit into 100 4 times, resulting in a remainder of 16.
Write down 4 as next digit of the result. 
Result so far: 38584.04
If we take 84 away from 100, we end up 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.

Going ahead to step 9:
The number 21 fits into 160 7 times, leaving a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 38584.047
If we take 147 away from 160, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 10:
21 goes into 130 6 times with a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 38584.0476
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.

Let's proceed to step 11:
21 can be fit into 40 1 times, resulting in a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 38584.04761
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 12:
When dividing 190 by 21, we get 9 with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 38584.047619
The remainder is 1 after subtracting 189 from 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 13:
If we divide 10 by 21, we get 0 and a remainder of 10.
The next digit of our result is 0. 
Result so far: 38584.047619
If we take 0 away from 10, we end up 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.

On to step 14:
100 divided by 21 is 4 with a remainder of 16.
Write down 4 as next digit of the result. 
Result so far: 38584.04761904
Subtract 84 from 100 to 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.

Our division results in 38584.04761904 with a remaining 1.6e-08.