We're dividing 840834 by 21 
The aim is to understand the frequency of 21 in 840834.

Step 1:
When dividing 8 by 21, we get 0 with a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 8 after subtracting 0 from 8.
Bring next digit (4) of the dividend behind the 8 and repeat the process: 84 / 21

Let's proceed to step 2:
The number 21 fits into 84 4 times, leaving a remainder of 0.
Put 4 as the next digit of the answer. 
Result so far: 4.0
If we subtract 84 from 84, we get 0.
Grab the next digit (0) from the dividend, add it to 0, then carry on: 0 / 21

Let's proceed to step 3:
The number 21 fits into 0 0 times, leaving a remainder of 0.
The next digit of our result is 0. 
Result so far: 40.0
Subtract 0 from 0 to get 0.
Grab the next digit (8) from the dividend, add it to 0, then carry on: 8 / 21

Let's proceed to step 4:
21 goes into 8 0 times with a remainder of 8.
The next digit of our result is 0. 
Result so far: 400.0
The remainder is 8 after subtracting 0 from 8.
Grab the next digit (3) from the dividend, add it to 8, then carry on: 83 / 21

Moving on to step 5:
21 can be fit into 83 3 times, resulting in a remainder of 20.
The number 3 becomes the next digit in our result. 
Result so far: 4003.0
Subtracting 63 from 83 leaves us with 20.
Append the next digit (4) from the dividend to 20 and continue with: 204 / 21

Moving on to step 6:
21 goes into 204 9 times with a remainder of 15.
Write down 9 as next digit of the result. 
Result so far: 40039.0
If we take 189 away from 204, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

On to step 7:
If we divide 150 by 21, we get 7 and a remainder of 3.
The next digit of our result is 7. 
Result so far: 40039.7
If we subtract 147 from 150, we get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Step 8:
When dividing 30 by 21, we get 1 with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 40039.71
Deduct 21 from 30 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Step 9:
When dividing 90 by 21, we get 4 with a remainder of 6.
The next digit of our result is 4. 
Result so far: 40039.714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 10:
21 goes into 60 2 times with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 40039.7142
Deduct 42 from 60 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 11:
21 goes into 180 8 times with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 40039.71428
If we subtract 168 from 180, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Let's proceed to step 12:
If we divide 120 by 21, we get 5 and a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 40039.714285
If we take 105 away from 120, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 13:
21 goes into 150 7 times with a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 40039.7142857
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Going ahead to step 14:
30 divided by 21 is 1 with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 40039.71428571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

The quotient of the division is 40039.71428571, and the remainder is 9e-09.