Let's divide 124397 by 21
The aim is to understand the frequency of 21 in 124397.

Advancing to step 1:
If we divide 1 by 21, we get 0 and a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (2) from the dividend after 1, then repeat: 12 / 21

Moving on to step 2:
The number 21 fits into 12 0 times, leaving a remainder of 12.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 12 and we're left with 12.
Append the next digit (4) from the dividend to 12 and continue with: 124 / 21

Moving on to step 3:
If we divide 124 by 21, we get 5 and a remainder of 19.
Put 5 as the next digit of the answer. 
Result so far: 5.0
If we take 105 away from 124, we end up with 19.
Include the next digit (3) from the dividend after 19, then repeat: 193 / 21

Advancing to step 4:
The number 21 fits into 193 9 times, leaving a remainder of 4.
Use 9 as the next digit of our solution. 
Result so far: 59.0
If we subtract 189 from 193, we get 4.
Bring next digit (9) of the dividend behind the 4 and repeat the process: 49 / 21

Going ahead to step 5:
49 divided by 21 is 2 with a remainder of 7.
Use 2 as the next digit of our solution. 
Result so far: 592.0
If we subtract 42 from 49, we get 7.
Take the next digit (7) from the dividend and append it to 7, then repeat: 77 / 21

Moving on to step 6:
21 goes into 77 3 times with a remainder of 14.
Record the quotient 3 as the next digit in the result. 
Result so far: 5923.0
Deduct 63 from 77 and we're left with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Advancing to step 7:
21 goes into 140 6 times with a remainder of 14.
Put 6 as the next digit of the answer. 
Result so far: 5923.6
Subtract 126 from 140 to get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Let's proceed to step 8:
If we divide 140 by 21, we get 6 and a remainder of 14.
The next digit of our result is 6. 
Result so far: 5923.66
The remainder is 14 after subtracting 126 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

After the division, we end up with 5923.66 and a remainder of 0.014.