284178 divided by 21 
The aim is to understand the frequency of 21 in 284178.

Step 1:
2 divided by 21 is 0 with a remainder of 2.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 2 and we're left with 2.
Fetch the next digit (8) from the dividend, attach it to 2 and continue: 28 / 21

Going ahead to step 2:
28 divided by 21 is 1 with a remainder of 7.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
If we subtract 21 from 28, we get 7.
Fetch the next digit (4) from the dividend, attach it to 7 and continue: 74 / 21

Moving on to step 3:
The number 21 fits into 74 3 times, leaving a remainder of 11.
The number 3 becomes the next digit in our result. 
Result so far: 13.0
Deduct 63 from 74 and we're left with 11.
Fetch the next digit (1) from the dividend, attach it to 11 and continue: 111 / 21

Let's proceed to step 4:
21 can be fit into 111 5 times, resulting in a remainder of 6.
The number 5 becomes the next digit in our result. 
Result so far: 135.0
If we subtract 105 from 111, we get 6.
Take the next digit (7) from the dividend and append it to 6, then repeat: 67 / 21

On to step 5:
The number 21 fits into 67 3 times, leaving a remainder of 4.
The next digit of our result is 3. 
Result so far: 1353.0
If we subtract 63 from 67, we get 4.
Take the next digit (8) from the dividend and append it to 4, then repeat: 48 / 21

Moving on to step 6:
21 goes into 48 2 times with a remainder of 6.
Put 2 as the next digit of the answer. 
Result so far: 13532.0
Deduct 42 from 48 and we're left 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.

Going ahead to step 7:
When dividing 60 by 21, we get 2 with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 13532.2
If we take 42 away from 60, we end up 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.

On to step 8:
180 divided by 21 is 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 13532.28
If we subtract 168 from 180, we 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 9:
If we divide 120 by 21, we get 5 and a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 13532.285
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 10:
The number 21 fits into 150 7 times, leaving a remainder of 3.
The next digit of our result is 7. 
Result so far: 13532.2857
Subtracting 147 from 150 leaves us with 3.
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 11:
30 divided by 21 is 1 with a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 13532.28571
Deduct 21 from 30 and we're left with 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 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: 13532.285714
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.

Step 13:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 13532.2857142
If we subtract 42 from 60, we 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:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 13532.28571428
If we subtract 168 from 180, we 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.

The final result is 13532.28571428 with a remainder of 1.2e-08.