Let's divide 450435 by 21
The aim is to understand the frequency of 21 in 450435.

Step 1:
4 divided by 21 is 0 with a remainder of 4.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 4, we end up with 4.
Take the next digit (5) from the dividend and append it to 4, then repeat: 45 / 21

Advancing to step 2:
When dividing 45 by 21, we get 2 with a remainder of 3.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
The remainder is 3 after subtracting 42 from 45.
Grab the next digit (0) from the dividend, add it to 3, then carry on: 30 / 21

On to step 3:
If we divide 30 by 21, we get 1 and a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 21.0
Subtract 21 from 30 to get 9.
Append the next digit (4) from the dividend to 9 and continue with: 94 / 21

Going ahead to step 4:
21 goes into 94 4 times with a remainder of 10.
Use 4 as the next digit of our solution. 
Result so far: 214.0
Deduct 84 from 94 and we're left with 10.
Grab the next digit (3) from the dividend, add it to 10, then carry on: 103 / 21

Moving on to step 5:
When dividing 103 by 21, we get 4 with a remainder of 19.
The next digit of our result is 4. 
Result so far: 2144.0
Subtracting 84 from 103 leaves us with 19.
Fetch the next digit (5) from the dividend, attach it to 19 and continue: 195 / 21

Moving on to step 6:
The number 21 fits into 195 9 times, leaving a remainder of 6.
Put 9 as the next digit of the answer. 
Result so far: 21449.0
Subtracting 189 from 195 leaves us with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Let's proceed to step 7:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 21449.2
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 8:
When dividing 180 by 21, we get 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 21449.28
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 9:
When dividing 120 by 21, we get 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 21449.285
If we subtract 105 from 120, we get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 10:
21 can be fit into 150 7 times, resulting in a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 21449.2857
If we subtract 147 from 150, we get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 11:
21 goes into 30 1 times with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 21449.28571
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.

Advancing to step 12:
21 can be fit into 90 4 times, resulting in a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 21449.285714
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.

On to step 13:
21 goes into 60 2 times with a remainder of 18.
The next digit of our result is 2. 
Result so far: 21449.2857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Moving on to step 14:
If we divide 180 by 21, we get 8 and a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 21449.28571428
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

In conclusion, the division gives 21449.28571428 with a balance of 1.2e-08.