We look at the division of 136979 by 21 
The aim is to understand the frequency of 21 in 136979.

Step 1:
21 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Bring next digit (3) of the dividend behind the 1 and repeat the process: 13 / 21

Moving on to step 2:
13 divided by 21 is 0 with a remainder of 13.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 13 and we're left with 13.
Fetch the next digit (6) from the dividend, attach it to 13 and continue: 136 / 21

Advancing to step 3:
21 can be fit into 136 6 times, resulting in a remainder of 10.
The number 6 becomes the next digit in our result. 
Result so far: 6.0
The remainder is 10 after subtracting 126 from 136.
Fetch the next digit (9) from the dividend, attach it to 10 and continue: 109 / 21

Let's proceed to step 4:
If we divide 109 by 21, we get 5 and a remainder of 4.
Use 5 as the next digit of our solution. 
Result so far: 65.0
Subtracting 105 from 109 leaves us with 4.
Grab the next digit (7) from the dividend, add it to 4, then carry on: 47 / 21

Going ahead to step 5:
47 divided by 21 is 2 with a remainder of 5.
The number 2 becomes the next digit in our result. 
Result so far: 652.0
The remainder is 5 after subtracting 42 from 47.
Fetch the next digit (9) from the dividend, attach it to 5 and continue: 59 / 21

On to step 6:
When dividing 59 by 21, we get 2 with a remainder of 17.
The next digit of our result is 2. 
Result so far: 6522.0
The remainder is 17 after subtracting 42 from 59.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

On to step 7:
If we divide 170 by 21, we get 8 and a remainder of 2.
The next digit of our result is 8. 
Result so far: 6522.8
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.

On to step 8:
If we divide 20 by 21, we get 0 and a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 6522.8
If we take 0 away from 20, we end up 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.

Step 9:
200 divided by 21 is 9 with a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 6522.809
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Moving on to step 10:
21 can be fit into 110 5 times, resulting in a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 6522.8095
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.

Moving on to step 11:
When dividing 50 by 21, we get 2 with a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 6522.80952
If we take 42 away from 50, we end up 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.

On to step 12:
21 goes into 80 3 times with a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 6522.809523
Subtracting 63 from 80 leaves us 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 13:
21 can be fit into 170 8 times, resulting in a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 6522.8095238
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.

Let's proceed to step 14:
The number 21 fits into 20 0 times, leaving a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 6522.8095238
If we take 0 away from 20, we end up 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.

In conclusion, the division gives 6522.8095238 with a balance of 2e-08.