We look at the division of 899716 by 21 
The aim is to understand the frequency of 21 in 899716.

Moving on to step 1:
When dividing 8 by 21, we get 0 with a remainder of 8.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Fetch the next digit (9) from the dividend, attach it to 8 and continue: 89 / 21

Going ahead to step 2:
The number 21 fits into 89 4 times, leaving a remainder of 5.
Use 4 as the next digit of our solution. 
Result so far: 4.0
Deduct 84 from 89 and we're left with 5.
Append the next digit (9) from the dividend to 5 and continue with: 59 / 21

On to step 3:
59 divided by 21 is 2 with a remainder of 17.
The number 2 becomes the next digit in our result. 
Result so far: 42.0
If we take 42 away from 59, we end up with 17.
Fetch the next digit (7) from the dividend, attach it to 17 and continue: 177 / 21

Moving on to step 4:
177 divided by 21 is 8 with a remainder of 9.
Write down 8 as next digit of the result. 
Result so far: 428.0
If we take 168 away from 177, we end up with 9.
Bring next digit (1) of the dividend behind the 9 and repeat the process: 91 / 21

On to step 5:
When dividing 91 by 21, we get 4 with a remainder of 7.
The next digit of our result is 4. 
Result so far: 4284.0
If we subtract 84 from 91, we get 7.
Bring next digit (6) of the dividend behind the 7 and repeat the process: 76 / 21

On to step 6:
When dividing 76 by 21, we get 3 with a remainder of 13.
The next digit of our result is 3. 
Result so far: 42843.0
Subtracting 63 from 76 leaves us 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.

Step 7:
When dividing 130 by 21, we get 6 with a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 42843.6
The remainder is 4 after subtracting 126 from 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 8:
21 goes into 40 1 times with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 42843.61
Subtracting 21 from 40 leaves us with 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 9:
21 goes into 190 9 times with a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 42843.619
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.

Moving on to step 10:
The number 21 fits into 10 0 times, leaving a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 42843.619
Subtracting 0 from 10 leaves us 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.

Moving on to step 11:
21 goes into 100 4 times with a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 42843.61904
Deduct 84 from 100 and we're left 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.

Advancing to step 12:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 42843.619047
Subtract 147 from 160 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Let's proceed to step 13:
21 can be fit into 130 6 times, resulting in a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 42843.6190476
Subtracting 126 from 130 leaves us with 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 14:
21 goes into 40 1 times with a remainder of 19.
The next digit of our result is 1. 
Result so far: 42843.61904761
Subtracting 21 from 40 leaves us with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

The final outcome is 42843.61904761, with a leftover of 1.9e-08.