376260 divided by 21 
The aim is to understand the frequency of 21 in 376260.

Advancing to step 1:
3 divided by 21 is 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Include the next digit (7) from the dividend after 3, then repeat: 37 / 21

Step 2:
The number 21 fits into 37 1 times, leaving a remainder of 16.
The next digit of our result is 1. 
Result so far: 1.0
If we subtract 21 from 37, we get 16.
Bring next digit (6) of the dividend behind the 16 and repeat the process: 166 / 21

Moving on to step 3:
21 goes into 166 7 times with a remainder of 19.
The number 7 becomes the next digit in our result. 
Result so far: 17.0
If we subtract 147 from 166, we get 19.
Grab the next digit (2) from the dividend, add it to 19, then carry on: 192 / 21

Advancing to step 4:
21 can be fit into 192 9 times, resulting in a remainder of 3.
Write down 9 as next digit of the result. 
Result so far: 179.0
The remainder is 3 after subtracting 189 from 192.
Bring next digit (6) of the dividend behind the 3 and repeat the process: 36 / 21

Let's proceed to step 5:
36 divided by 21 is 1 with a remainder of 15.
Use 1 as the next digit of our solution. 
Result so far: 1791.0
Subtract 21 from 36 to get 15.
Fetch the next digit (0) from the dividend, attach it to 15 and continue: 150 / 21

On to step 6:
If we divide 150 by 21, we get 7 and a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 17917.0
If we take 147 away from 150, we end up 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.

Advancing to step 7:
If we divide 30 by 21, we get 1 and a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 17917.1
If we take 21 away from 30, we end up 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 8:
21 goes into 90 4 times with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 17917.14
Deduct 84 from 90 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.

Moving on to step 9:
21 goes into 60 2 times with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 17917.142
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.

Going ahead to step 10:
21 can be fit into 180 8 times, resulting in a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 17917.1428
Subtracting 168 from 180 leaves us 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.

Going ahead to step 11:
The number 21 fits into 120 5 times, leaving a remainder of 15.
The next digit of our result is 5. 
Result so far: 17917.14285
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.

Let's proceed to step 12:
When dividing 150 by 21, we get 7 with a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 17917.142857
If we subtract 147 from 150, we 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.

Going ahead to step 13:
30 divided by 21 is 1 with a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 17917.1428571
If we subtract 21 from 30, we get 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 14:
21 goes into 90 4 times with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 17917.14285714
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.

Our division results in 17917.14285714 with a remaining 6e-09.