We look at the division of 98990532 by 21 
The aim is to understand the frequency of 21 in 98990532.

On to step 1:
21 goes into 9 0 times with a remainder of 9.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 9 to get 9.
Include the next digit (8) from the dividend after 9, then repeat: 98 / 21

On to step 2:
The number 21 fits into 98 4 times, leaving a remainder of 14.
The next digit of our result is 4. 
Result so far: 4.0
Subtracting 84 from 98 leaves us with 14.
Fetch the next digit (9) from the dividend, attach it to 14 and continue: 149 / 21

Going ahead to step 3:
21 can be fit into 149 7 times, resulting in a remainder of 2.
Write down 7 as next digit of the result. 
Result so far: 47.0
The remainder is 2 after subtracting 147 from 149.
Fetch the next digit (9) from the dividend, attach it to 2 and continue: 29 / 21

Step 4:
29 divided by 21 is 1 with a remainder of 8.
Record the quotient 1 as the next digit in the result. 
Result so far: 471.0
Subtract 21 from 29 to get 8.
Bring next digit (0) of the dividend behind the 8 and repeat the process: 80 / 21

Let's proceed to step 5:
When dividing 80 by 21, we get 3 with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 4713.0
Deduct 63 from 80 and we're left with 17.
Fetch the next digit (5) from the dividend, attach it to 17 and continue: 175 / 21

Let's proceed to step 6:
21 can be fit into 175 8 times, resulting in a remainder of 7.
Put 8 as the next digit of the answer. 
Result so far: 47138.0
If we take 168 away from 175, we end up with 7.
Fetch the next digit (3) from the dividend, attach it to 7 and continue: 73 / 21

Going ahead to step 7:
The number 21 fits into 73 3 times, leaving a remainder of 10.
The next digit of our result is 3. 
Result so far: 471383.0
Subtract 63 from 73 to get 10.
Bring next digit (2) of the dividend behind the 10 and repeat the process: 102 / 21

Advancing to step 8:
102 divided by 21 is 4 with a remainder of 18.
Record the quotient 4 as the next digit in the result. 
Result so far: 4713834.0
Subtract 84 from 102 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.

Moving on to step 9:
If we divide 180 by 21, we get 8 and a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 4713834.8
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.

On to step 10:
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: 4713834.85
If we subtract 105 from 120, we get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 11:
150 divided by 21 is 7 with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 4713834.857
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.

Step 12:
21 goes into 30 1 times with a remainder of 9.
The next digit of our result is 1. 
Result so far: 4713834.8571
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.

Advancing to step 13:
21 can be fit into 90 4 times, resulting in a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 4713834.85714
Deduct 84 from 90 and we're left 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 14:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 4713834.857142
The remainder is 18 after subtracting 42 from 60.
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 15:
21 goes into 180 8 times with a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 4713834.8571428
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.

Advancing to step 16:
21 goes into 120 5 times with a remainder of 15.
The next digit of our result is 5. 
Result so far: 4713834.85714285
Deduct 105 from 120 and we're left 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.

The final result is 4713834.85714285 with a remainder of 1.5e-08.