Let's divide 660853 by 21
The aim is to understand the frequency of 21 in 660853.

Going ahead to step 1:
When dividing 6 by 21, we get 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Append the next digit (6) from the dividend to 6 and continue with: 66 / 21

Going ahead to step 2:
If we divide 66 by 21, we get 3 and a remainder of 3.
Write down 3 as next digit of the result. 
Result so far: 3.0
The remainder is 3 after subtracting 63 from 66.
Take the next digit (0) from the dividend and append it to 3, then repeat: 30 / 21

Step 3:
30 divided by 21 is 1 with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 31.0
If we take 21 away from 30, we end up with 9.
Take the next digit (8) from the dividend and append it to 9, then repeat: 98 / 21

Going ahead to step 4:
98 divided by 21 is 4 with a remainder of 14.
Put 4 as the next digit of the answer. 
Result so far: 314.0
The remainder is 14 after subtracting 84 from 98.
Include the next digit (5) from the dividend after 14, then repeat: 145 / 21

Step 5:
21 can be fit into 145 6 times, resulting in a remainder of 19.
The next digit of our result is 6. 
Result so far: 3146.0
Deduct 126 from 145 and we're left with 19.
Append the next digit (3) from the dividend to 19 and continue with: 193 / 21

Going ahead to step 6:
21 can be fit into 193 9 times, resulting in a remainder of 4.
The next digit of our result is 9. 
Result so far: 31469.0
Subtracting 189 from 193 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.

Let's proceed to step 7:
When dividing 40 by 21, we get 1 with a remainder of 19.
The next digit of our result is 1. 
Result so far: 31469.1
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.

Going ahead to step 8:
21 goes into 190 9 times with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 31469.19
If we take 189 away from 190, we end up with 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 9:
21 goes into 10 0 times with a remainder of 10.
The next digit of our result is 0. 
Result so far: 31469.19
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.

Moving on to step 10:
If we divide 100 by 21, we get 4 and a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 31469.1904
Subtracting 84 from 100 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

On to step 11:
21 goes into 160 7 times with a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 31469.19047
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 12:
The number 21 fits into 130 6 times, leaving a remainder of 4.
The next digit of our result is 6. 
Result so far: 31469.190476
Subtract 126 from 130 to get 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 13:
If we divide 40 by 21, we get 1 and a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 31469.1904761
The remainder is 19 after subtracting 21 from 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

On to step 14:
21 goes into 190 9 times with a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 31469.19047619
The remainder is 1 after subtracting 189 from 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

The final result is 31469.19047619 with a remainder of 1e-09.