We divide 391471 by 21
The aim is to understand the frequency of 21 in 391471.

Step 1:
When dividing 3 by 21, we get 0 with a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Include the next digit (9) from the dividend after 3, then repeat: 39 / 21

On to step 2:
21 can be fit into 39 1 times, resulting in a remainder of 18.
The next digit of our result is 1. 
Result so far: 1.0
If we take 21 away from 39, we end up with 18.
Fetch the next digit (1) from the dividend, attach it to 18 and continue: 181 / 21

Moving on to step 3:
181 divided by 21 is 8 with a remainder of 13.
Use 8 as the next digit of our solution. 
Result so far: 18.0
Subtract 168 from 181 to get 13.
Fetch the next digit (4) from the dividend, attach it to 13 and continue: 134 / 21

Let's proceed to step 4:
The number 21 fits into 134 6 times, leaving a remainder of 8.
Write down 6 as next digit of the result. 
Result so far: 186.0
Subtract 126 from 134 to get 8.
Fetch the next digit (7) from the dividend, attach it to 8 and continue: 87 / 21

Going ahead to step 5:
21 goes into 87 4 times with a remainder of 3.
Put 4 as the next digit of the answer. 
Result so far: 1864.0
The remainder is 3 after subtracting 84 from 87.
Fetch the next digit (1) from the dividend, attach it to 3 and continue: 31 / 21

Advancing to step 6:
The number 21 fits into 31 1 times, leaving a remainder of 10.
Use 1 as the next digit of our solution. 
Result so far: 18641.0
The remainder is 10 after subtracting 21 from 31.
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:
21 can be fit into 100 4 times, resulting in a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 18641.4
Subtract 84 from 100 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Moving on to step 8:
If we divide 160 by 21, we get 7 and a remainder of 13.
The next digit of our result is 7. 
Result so far: 18641.47
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.

Moving on to step 9:
When dividing 130 by 21, we get 6 with a remainder of 4.
The next digit of our result is 6. 
Result so far: 18641.476
Subtracting 126 from 130 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 10:
21 goes into 40 1 times with a remainder of 19.
Record the quotient 1 as the next digit in the result. 
Result so far: 18641.4761
Deduct 21 from 40 and we're left with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Moving on to step 11:
21 goes into 190 9 times with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 18641.47619
Subtract 189 from 190 to get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Step 12:
10 divided by 21 is 0 with a remainder of 10.
Write down 0 as next digit of the result. 
Result so far: 18641.47619
Subtracting 0 from 10 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On 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: 18641.4761904
If we subtract 84 from 100, we get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Moving on to step 14:
160 divided by 21 is 7 with a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 18641.47619047
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.

The quotient of the division is 18641.47619047, and the remainder is 1.3e-08.