89977131 divided by 21 
The aim is to understand the frequency of 21 in 89977131.

Let's proceed to step 1:
8 divided by 21 is 0 with a remainder of 8.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Include the next digit (9) from the dividend after 8, then repeat: 89 / 21

Advancing to step 2:
89 divided by 21 is 4 with a remainder of 5.
The number 4 becomes the next digit in our result. 
Result so far: 4.0
Subtract 84 from 89 to get 5.
Bring next digit (9) of the dividend behind the 5 and repeat the process: 59 / 21

Let's proceed to step 3:
If we divide 59 by 21, we get 2 and a remainder of 17.
The number 2 becomes the next digit in our result. 
Result so far: 42.0
Subtracting 42 from 59 leaves us with 17.
Append the next digit (7) from the dividend to 17 and continue with: 177 / 21

Moving on to step 4:
21 can be fit into 177 8 times, resulting in a remainder of 9.
Put 8 as the next digit of the answer. 
Result so far: 428.0
Deduct 168 from 177 and we're left with 9.
Take the next digit (7) from the dividend and append it to 9, then repeat: 97 / 21

Step 5:
21 can be fit into 97 4 times, resulting in a remainder of 13.
Use 4 as the next digit of our solution. 
Result so far: 4284.0
The remainder is 13 after subtracting 84 from 97.
Append the next digit (1) from the dividend to 13 and continue with: 131 / 21

Going ahead to step 6:
21 can be fit into 131 6 times, resulting in a remainder of 5.
The number 6 becomes the next digit in our result. 
Result so far: 42846.0
Subtracting 126 from 131 leaves us with 5.
Bring next digit (3) of the dividend behind the 5 and repeat the process: 53 / 21

On to step 7:
21 goes into 53 2 times with a remainder of 11.
Record the quotient 2 as the next digit in the result. 
Result so far: 428462.0
Subtracting 42 from 53 leaves us with 11.
Take the next digit (1) from the dividend and append it to 11, then repeat: 111 / 21

On to step 8:
21 can be fit into 111 5 times, resulting in a remainder of 6.
Put 5 as the next digit of the answer. 
Result so far: 4284625.0
Subtract 105 from 111 to get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Let's proceed to step 9:
60 divided by 21 is 2 with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 4284625.2
Subtracting 42 from 60 leaves us 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.

Moving on to step 10:
180 divided by 21 is 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 4284625.28
Subtracting 168 from 180 leaves us with 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 11:
120 divided by 21 is 5 with a remainder of 15.
The next digit of our result is 5. 
Result so far: 4284625.285
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.

Going ahead to step 12:
150 divided by 21 is 7 with a remainder of 3.
The next digit of our result is 7. 
Result so far: 4284625.2857
Deduct 147 from 150 and we're left with 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 13:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 4284625.28571
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.

Step 14:
When dividing 90 by 21, we get 4 with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 4284625.285714
Subtracting 84 from 90 leaves us 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.

Going ahead to step 15:
60 divided by 21 is 2 with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 4284625.2857142
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.

Advancing to step 16:
The number 21 fits into 180 8 times, leaving a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 4284625.28571428
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

In conclusion, the division gives 4284625.28571428 with a balance of 1.2e-08.