929991 divided by 21 
The aim is to understand the frequency of 21 in 929991.

Advancing to step 1:
9 divided by 21 is 0 with a remainder of 9.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 9 to get 9.
Include the next digit (2) from the dividend after 9, then repeat: 92 / 21

Step 2:
92 divided by 21 is 4 with a remainder of 8.
The next digit of our result is 4. 
Result so far: 4.0
Subtracting 84 from 92 leaves us with 8.
Include the next digit (9) from the dividend after 8, then repeat: 89 / 21

Going ahead to step 3:
89 divided by 21 is 4 with a remainder of 5.
Use 4 as the next digit of our solution. 
Result so far: 44.0
Subtracting 84 from 89 leaves us with 5.
Append the next digit (9) from the dividend to 5 and continue with: 59 / 21

Let's proceed to step 4:
If we divide 59 by 21, we get 2 and a remainder of 17.
Record the quotient 2 as the next digit in the result. 
Result so far: 442.0
Deduct 42 from 59 and we're left with 17.
Fetch the next digit (9) from the dividend, attach it to 17 and continue: 179 / 21

On to step 5:
179 divided by 21 is 8 with a remainder of 11.
Record the quotient 8 as the next digit in the result. 
Result so far: 4428.0
Subtract 168 from 179 to get 11.
Include the next digit (1) from the dividend after 11, then repeat: 111 / 21

Going ahead to step 6:
When dividing 111 by 21, we get 5 with a remainder of 6.
The next digit of our result is 5. 
Result so far: 44285.0
If we take 105 away from 111, we end up with 6.
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 7:
The number 21 fits into 60 2 times, leaving a remainder of 18.
The next digit of our result is 2. 
Result so far: 44285.2
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 8:
180 divided by 21 is 8 with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 44285.28
Subtract 168 from 180 to 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.

Going ahead to step 9:
120 divided by 21 is 5 with a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 44285.285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 10:
150 divided by 21 is 7 with a remainder of 3.
The next digit of our result is 7. 
Result so far: 44285.2857
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.

Let's proceed to step 11:
21 goes into 30 1 times with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 44285.28571
Subtracting 21 from 30 leaves us 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.

Advancing to step 12:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 44285.285714
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.

Advancing to step 13:
21 goes into 60 2 times with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 44285.2857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Let's proceed to step 14:
When dividing 180 by 21, we get 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 44285.28571428
Subtract 168 from 180 to 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.

The final result is 44285.28571428 with a remainder of 1.2e-08.