We're dividing 920840 by 21 
The aim is to understand the frequency of 21 in 920840.

On to step 1:
The number 21 fits into 9 0 times, leaving a remainder of 9.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 9 to get 9.
Bring next digit (2) of the dividend behind the 9 and repeat the process: 92 / 21

Going ahead to step 2:
21 goes into 92 4 times with a remainder of 8.
The next digit of our result is 4. 
Result so far: 4.0
Deduct 84 from 92 and we're left with 8.
Bring next digit (0) of the dividend behind the 8 and repeat the process: 80 / 21

Going ahead to step 3:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 43.0
Deduct 63 from 80 and we're left with 17.
Grab the next digit (8) from the dividend, add it to 17, then carry on: 178 / 21

Advancing to step 4:
The number 21 fits into 178 8 times, leaving a remainder of 10.
Write down 8 as next digit of the result. 
Result so far: 438.0
If we take 168 away from 178, we end up with 10.
Fetch the next digit (4) from the dividend, attach it to 10 and continue: 104 / 21

Moving on to step 5:
When dividing 104 by 21, we get 4 with a remainder of 20.
Record the quotient 4 as the next digit in the result. 
Result so far: 4384.0
If we take 84 away from 104, we end up with 20.
Bring next digit (0) of the dividend behind the 20 and repeat the process: 200 / 21

Advancing to step 6:
200 divided by 21 is 9 with a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 43849.0
Subtract 189 from 200 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Let's proceed to step 7:
When dividing 110 by 21, we get 5 with a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 43849.5
Deduct 105 from 110 and we're left 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.

Let's proceed to step 8:
When dividing 50 by 21, we get 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 43849.52
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Advancing to step 9:
80 divided by 21 is 3 with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 43849.523
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.

Moving on to step 10:
21 goes into 170 8 times with a remainder of 2.
Put 8 as the next digit of the answer. 
Result so far: 43849.5238
Subtracting 168 from 170 leaves us 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.

Moving on to step 11:
20 divided by 21 is 0 with a remainder of 20.
The next digit of our result is 0. 
Result so far: 43849.5238
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.

Let's proceed to step 12:
200 divided by 21 is 9 with a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 43849.523809
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.

Let's proceed to step 13:
21 goes into 110 5 times with a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 43849.5238095
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Step 14:
When dividing 50 by 21, we get 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 43849.52380952
Subtract 42 from 50 to 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.

The final outcome is 43849.52380952, with a leftover of 8e-09.