Let's divide 129146 by 21
The aim is to understand the frequency of 21 in 129146.

Advancing to step 1:
When dividing 1 by 21, we get 0 with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 1, we end up with 1.
Include the next digit (2) from the dividend after 1, then repeat: 12 / 21

Going ahead to step 2:
When dividing 12 by 21, we get 0 with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 12, we get 12.
Grab the next digit (9) from the dividend, add it to 12, then carry on: 129 / 21

On to step 3:
If we divide 129 by 21, we get 6 and a remainder of 3.
The number 6 becomes the next digit in our result. 
Result so far: 6.0
If we take 126 away from 129, we end up with 3.
Include the next digit (1) from the dividend after 3, then repeat: 31 / 21

Moving on to step 4:
If we divide 31 by 21, we get 1 and a remainder of 10.
The next digit of our result is 1. 
Result so far: 61.0
Deduct 21 from 31 and we're left with 10.
Append the next digit (4) from the dividend to 10 and continue with: 104 / 21

On to step 5:
104 divided by 21 is 4 with a remainder of 20.
The number 4 becomes the next digit in our result. 
Result so far: 614.0
Subtract 84 from 104 to get 20.
Bring next digit (6) of the dividend behind the 20 and repeat the process: 206 / 21

Going ahead to step 6:
When dividing 206 by 21, we get 9 with a remainder of 17.
Put 9 as the next digit of the answer. 
Result so far: 6149.0
If we take 189 away from 206, we end up 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.

Step 7:
21 can be fit into 170 8 times, resulting in a remainder of 2.
The next digit of our result is 8. 
Result so far: 6149.8
If we take 168 away from 170, we end up 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.

Going ahead to step 8:
21 can be fit into 20 0 times, resulting in a remainder of 20.
The next digit of our result is 0. 
Result so far: 6149.8
The remainder is 20 after subtracting 0 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 9:
The number 21 fits into 200 9 times, leaving a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 6149.809
Subtracting 189 from 200 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 10:
21 goes into 110 5 times with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 6149.8095
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:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 6149.80952
Subtract 42 from 50 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 12:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 6149.809523
Deduct 63 from 80 and we're left 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.

Going ahead to step 13:
When dividing 170 by 21, we get 8 with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 6149.8095238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 14:
21 goes into 20 0 times with a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 6149.8095238
Subtracting 0 from 20 leaves us 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.

Our division results in 6149.8095238 with a remaining 2e-08.