We're dividing 451709 by 21 
The aim is to understand the frequency of 21 in 451709.

Going ahead to step 1:
21 can be fit into 4 0 times, resulting in a remainder of 4.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 4, we get 4.
Include the next digit (5) from the dividend after 4, then repeat: 45 / 21

Step 2:
21 goes into 45 2 times with a remainder of 3.
Put 2 as the next digit of the answer. 
Result so far: 2.0
Subtracting 42 from 45 leaves us with 3.
Grab the next digit (1) from the dividend, add it to 3, then carry on: 31 / 21

Going ahead to step 3:
If we divide 31 by 21, we get 1 and a remainder of 10.
The number 1 becomes the next digit in our result. 
Result so far: 21.0
Deduct 21 from 31 and we're left with 10.
Fetch the next digit (7) from the dividend, attach it to 10 and continue: 107 / 21

Advancing to step 4:
When dividing 107 by 21, we get 5 with a remainder of 2.
Record the quotient 5 as the next digit in the result. 
Result so far: 215.0
If we take 105 away from 107, we end up with 2.
Grab the next digit (0) from the dividend, add it to 2, then carry on: 20 / 21

Going ahead to step 5:
If we divide 20 by 21, we get 0 and a remainder of 20.
The next digit of our result is 0. 
Result so far: 2150.0
Subtracting 0 from 20 leaves us with 20.
Fetch the next digit (9) from the dividend, attach it to 20 and continue: 209 / 21

Step 6:
When dividing 209 by 21, we get 9 with a remainder of 20.
Put 9 as the next digit of the answer. 
Result so far: 21509.0
If we subtract 189 from 209, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 7:
200 divided by 21 is 9 with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 21509.9
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Let's proceed to step 8:
21 goes into 110 5 times with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 21509.95
Subtract 105 from 110 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 9:
21 can be fit into 50 2 times, resulting in a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 21509.952
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 10:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 21509.9523
Deduct 63 from 80 and we're left with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Let's proceed to step 11:
21 goes into 170 8 times with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 21509.95238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 12:
If we divide 20 by 21, we get 0 and a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 21509.95238
If we subtract 0 from 20, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 13:
21 can be fit into 200 9 times, resulting in a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 21509.9523809
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 14:
When dividing 110 by 21, we get 5 with a remainder of 5.
The next digit of our result is 5. 
Result so far: 21509.95238095
If we take 105 away from 110, we end up with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

The quotient of the division is 21509.95238095, and the remainder is 5e-09.