We look at the division of 542322 by 21 
The aim is to understand the frequency of 21 in 542322.

Let's proceed to step 1:
5 divided by 21 is 0 with a remainder of 5.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 5, we end up with 5.
Grab the next digit (4) from the dividend, add it to 5, then carry on: 54 / 21

Let's proceed to step 2:
54 divided by 21 is 2 with a remainder of 12.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
If we subtract 42 from 54, we get 12.
Bring next digit (2) of the dividend behind the 12 and repeat the process: 122 / 21

Moving on to step 3:
The number 21 fits into 122 5 times, leaving a remainder of 17.
Use 5 as the next digit of our solution. 
Result so far: 25.0
The remainder is 17 after subtracting 105 from 122.
Take the next digit (3) from the dividend and append it to 17, then repeat: 173 / 21

Let's proceed to step 4:
21 goes into 173 8 times with a remainder of 5.
Record the quotient 8 as the next digit in the result. 
Result so far: 258.0
If we take 168 away from 173, we end up with 5.
Take the next digit (2) from the dividend and append it to 5, then repeat: 52 / 21

Let's proceed to step 5:
21 goes into 52 2 times with a remainder of 10.
The next digit of our result is 2. 
Result so far: 2582.0
If we subtract 42 from 52, we get 10.
Append the next digit (2) from the dividend to 10 and continue with: 102 / 21

On to step 6:
The number 21 fits into 102 4 times, leaving a remainder of 18.
Put 4 as the next digit of the answer. 
Result so far: 25824.0
Deduct 84 from 102 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 7:
The number 21 fits into 180 8 times, leaving a remainder of 12.
The next digit of our result is 8. 
Result so far: 25824.8
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 8:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 25824.85
Subtracting 105 from 120 leaves us 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.

Let's proceed to step 9:
150 divided by 21 is 7 with a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 25824.857
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Going ahead to step 10:
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: 25824.8571
Subtract 21 from 30 to get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 11:
21 goes into 90 4 times with a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 25824.85714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 12:
The number 21 fits into 60 2 times, leaving a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 25824.857142
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 13:
21 goes into 180 8 times with a remainder of 12.
The next digit of our result is 8. 
Result so far: 25824.8571428
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 14:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 25824.85714285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

The final result is 25824.85714285 with a remainder of 1.5e-08.