Let's divide 423108 by 21
The aim is to understand the frequency of 21 in 423108.

Step 1:
21 goes into 4 0 times with a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 4 leaves us with 4.
Grab the next digit (2) from the dividend, add it to 4, then carry on: 42 / 21

Moving on to step 2:
The number 21 fits into 42 2 times, leaving a remainder of 0.
Use 2 as the next digit of our solution. 
Result so far: 2.0
If we subtract 42 from 42, we get 0.
Bring next digit (3) of the dividend behind the 0 and repeat the process: 3 / 21

Let's proceed to step 3:
3 divided by 21 is 0 with a remainder of 3.
Use 0 as the next digit of our solution. 
Result so far: 20.0
Subtract 0 from 3 to get 3.
Take the next digit (1) from the dividend and append it to 3, then repeat: 31 / 21

On to step 4:
When dividing 31 by 21, we get 1 with a remainder of 10.
Record the quotient 1 as the next digit in the result. 
Result so far: 201.0
The remainder is 10 after subtracting 21 from 31.
Grab the next digit (0) from the dividend, add it to 10, then carry on: 100 / 21

Let's proceed to step 5:
The number 21 fits into 100 4 times, leaving a remainder of 16.
The next digit of our result is 4. 
Result so far: 2014.0
Subtracting 84 from 100 leaves us with 16.
Bring next digit (8) of the dividend behind the 16 and repeat the process: 168 / 21

Let's proceed to step 6:
The number 21 fits into 168 8 times, leaving a remainder of 0.
Use 8 as the next digit of our solution. 
Result so far: 20148.0
If we subtract 168 from 168, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 7:
If we divide 0 by 21, we get 0 and a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 20148.0
Subtracting 0 from 0 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Step 8:
0 divided by 21 is 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 20148.0
Subtracting 0 from 0 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

After the division, we end up with 20148.0 and a remainder of 0.0.