We're dividing 450544 by 21 
The aim is to understand the frequency of 21 in 450544.

Moving on to step 1:
If we divide 4 by 21, we get 0 and a remainder of 4.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 4 after subtracting 0 from 4.
Append the next digit (5) from the dividend to 4 and continue with: 45 / 21

Advancing to step 2:
The number 21 fits into 45 2 times, leaving a remainder of 3.
Write down 2 as next digit of the result. 
Result so far: 2.0
Subtracting 42 from 45 leaves us with 3.
Include the next digit (0) from the dividend after 3, then repeat: 30 / 21

Let's proceed to step 3:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 21.0
Subtracting 21 from 30 leaves us with 9.
Take the next digit (5) from the dividend and append it to 9, then repeat: 95 / 21

Let's proceed to step 4:
21 goes into 95 4 times with a remainder of 11.
Write down 4 as next digit of the result. 
Result so far: 214.0
Deduct 84 from 95 and we're left with 11.
Take the next digit (4) from the dividend and append it to 11, then repeat: 114 / 21

Let's proceed to step 5:
When dividing 114 by 21, we get 5 with a remainder of 9.
The next digit of our result is 5. 
Result so far: 2145.0
If we subtract 105 from 114, we get 9.
Fetch the next digit (4) from the dividend, attach it to 9 and continue: 94 / 21

Moving on to step 6:
When dividing 94 by 21, we get 4 with a remainder of 10.
Write down 4 as next digit of the result. 
Result so far: 21454.0
Subtract 84 from 94 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 7:
100 divided by 21 is 4 with a remainder of 16.
The number 4 becomes the next digit in our result. 
Result so far: 21454.4
The remainder is 16 after subtracting 84 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 8:
21 goes into 160 7 times with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 21454.47
Subtracting 147 from 160 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 9:
21 goes into 130 6 times with a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 21454.476
Subtract 126 from 130 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

On to step 10:
21 can be fit into 40 1 times, resulting in a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 21454.4761
Subtract 21 from 40 to get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

On to step 11:
If we divide 190 by 21, we get 9 and a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 21454.47619
The remainder is 1 after subtracting 189 from 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

On to step 12:
When dividing 10 by 21, we get 0 with a remainder of 10.
Put 0 as the next digit of the answer. 
Result so far: 21454.47619
The remainder is 10 after subtracting 0 from 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 13:
21 goes into 100 4 times with a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 21454.4761904
Subtracting 84 from 100 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Step 14:
The number 21 fits into 160 7 times, leaving a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 21454.47619047
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

After the division, we end up with 21454.47619047 and a remainder of 1.3e-08.