687117 ÷ 21 
The aim is to understand the frequency of 21 in 687117.

Step 1:
21 goes into 6 0 times with a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Fetch the next digit (8) from the dividend, attach it to 6 and continue: 68 / 21

Advancing to step 2:
68 divided by 21 is 3 with a remainder of 5.
The next digit of our result is 3. 
Result so far: 3.0
Subtract 63 from 68 to get 5.
Fetch the next digit (7) from the dividend, attach it to 5 and continue: 57 / 21

Moving on to step 3:
21 goes into 57 2 times with a remainder of 15.
Use 2 as the next digit of our solution. 
Result so far: 32.0
The remainder is 15 after subtracting 42 from 57.
Bring next digit (1) of the dividend behind the 15 and repeat the process: 151 / 21

Going ahead to step 4:
The number 21 fits into 151 7 times, leaving a remainder of 4.
Use 7 as the next digit of our solution. 
Result so far: 327.0
Deduct 147 from 151 and we're left with 4.
Fetch the next digit (1) from the dividend, attach it to 4 and continue: 41 / 21

Advancing to step 5:
21 can be fit into 41 1 times, resulting in a remainder of 20.
Record the quotient 1 as the next digit in the result. 
Result so far: 3271.0
If we take 21 away from 41, we end up with 20.
Take the next digit (7) from the dividend and append it to 20, then repeat: 207 / 21

Advancing to step 6:
When dividing 207 by 21, we get 9 with a remainder of 18.
Record the quotient 9 as the next digit in the result. 
Result so far: 32719.0
Subtract 189 from 207 to 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 7:
When dividing 180 by 21, we get 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 32719.8
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.

Advancing to step 8:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 32719.85
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.

Step 9:
If we divide 150 by 21, we get 7 and a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 32719.857
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.

On to step 10:
The number 21 fits into 30 1 times, leaving a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 32719.8571
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.

Going ahead to step 11:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 32719.85714
Subtract 84 from 90 to get 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 12:
If we divide 60 by 21, we get 2 and a remainder of 18.
The next digit of our result is 2. 
Result so far: 32719.857142
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.

Moving on to step 13:
21 can be fit into 180 8 times, resulting in a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 32719.8571428
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.

Advancing to step 14:
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: 32719.85714285
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.

After the division, we end up with 32719.85714285 and a remainder of 1.5e-08.