Let's divide 906945 by 21
The aim is to understand the frequency of 21 in 906945.

Moving on to step 1:
21 can be fit into 9 0 times, resulting in a remainder of 9.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 9 and we're left with 9.
Bring next digit (0) of the dividend behind the 9 and repeat the process: 90 / 21

Going ahead to step 2:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 4.0
If we take 84 away from 90, we end up with 6.
Fetch the next digit (6) from the dividend, attach it to 6 and continue: 66 / 21

On to step 3:
21 goes into 66 3 times with a remainder of 3.
Use 3 as the next digit of our solution. 
Result so far: 43.0
Deduct 63 from 66 and we're left with 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 21

Moving on to step 4:
39 divided by 21 is 1 with a remainder of 18.
Use 1 as the next digit of our solution. 
Result so far: 431.0
If we take 21 away from 39, we end up with 18.
Append the next digit (4) from the dividend to 18 and continue with: 184 / 21

Let's proceed to step 5:
21 goes into 184 8 times with a remainder of 16.
The number 8 becomes the next digit in our result. 
Result so far: 4318.0
The remainder is 16 after subtracting 168 from 184.
Include the next digit (5) from the dividend after 16, then repeat: 165 / 21

Moving on to step 6:
21 goes into 165 7 times with a remainder of 18.
Record the quotient 7 as the next digit in the result. 
Result so far: 43187.0
If we take 147 away from 165, 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 7:
When dividing 180 by 21, we get 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 43187.8
If we take 168 away from 180, we end up 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.

Step 8:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 43187.85
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.

Advancing to step 9:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 43187.857
Subtract 147 from 150 to 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.

Moving on to step 10:
21 can be fit into 30 1 times, resulting in a remainder of 9.
The next digit of our result is 1. 
Result so far: 43187.8571
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.

Advancing to step 11:
21 goes into 90 4 times with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 43187.85714
If we take 84 away from 90, we end up 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.

Advancing to step 12:
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: 43187.857142
Deduct 42 from 60 and we're left 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.

Going ahead to step 13:
If we divide 180 by 21, we get 8 and a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 43187.8571428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 14:
If we divide 120 by 21, we get 5 and a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 43187.85714285
Subtract 105 from 120 to 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.

After the division, we end up with 43187.85714285 and a remainder of 1.5e-08.