We divide 408749 by 21
The aim is to understand the frequency of 21 in 408749.

Moving on to step 1:
When dividing 4 by 21, we get 0 with a remainder of 4.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 4 leaves us with 4.
Grab the next digit (0) from the dividend, add it to 4, then carry on: 40 / 21

Let's proceed to step 2:
If we divide 40 by 21, we get 1 and a remainder of 19.
The next digit of our result is 1. 
Result so far: 1.0
Subtracting 21 from 40 leaves us with 19.
Fetch the next digit (8) from the dividend, attach it to 19 and continue: 198 / 21

Going ahead to step 3:
The number 21 fits into 198 9 times, leaving a remainder of 9.
Record the quotient 9 as the next digit in the result. 
Result so far: 19.0
Subtract 189 from 198 to get 9.
Fetch the next digit (7) from the dividend, attach it to 9 and continue: 97 / 21

Moving on to step 4:
When dividing 97 by 21, we get 4 with a remainder of 13.
The number 4 becomes the next digit in our result. 
Result so far: 194.0
The remainder is 13 after subtracting 84 from 97.
Bring next digit (4) of the dividend behind the 13 and repeat the process: 134 / 21

Let's proceed to step 5:
21 goes into 134 6 times with a remainder of 8.
Put 6 as the next digit of the answer. 
Result so far: 1946.0
If we subtract 126 from 134, we get 8.
Fetch the next digit (9) from the dividend, attach it to 8 and continue: 89 / 21

Step 6:
If we divide 89 by 21, we get 4 and a remainder of 5.
Write down 4 as next digit of the result. 
Result so far: 19464.0
If we take 84 away from 89, 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.

Step 7:
If we divide 50 by 21, we get 2 and a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 19464.2
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 8:
When dividing 80 by 21, we get 3 with a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 19464.23
Subtracting 63 from 80 leaves us 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 9:
If we divide 170 by 21, we get 8 and a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 19464.238
If we take 168 away from 170, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 10:
21 goes into 20 0 times with a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 19464.238
Deduct 0 from 20 and we're left with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

On to step 11:
When dividing 200 by 21, we get 9 with a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 19464.23809
Deduct 189 from 200 and we're left with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 12:
110 divided by 21 is 5 with a remainder of 5.
The next digit of our result is 5. 
Result so far: 19464.238095
Deduct 105 from 110 and we're left 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.

On to step 13:
When dividing 50 by 21, we get 2 with a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 19464.2380952
If we take 42 away from 50, we end up 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 14:
When dividing 80 by 21, we get 3 with a remainder of 17.
Record the quotient 3 as the next digit in the result. 
Result so far: 19464.23809523
Subtracting 63 from 80 leaves us 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.

After the division, we end up with 19464.23809523 and a remainder of 1.7e-08.