We're dividing 716639 by 21 
The aim is to understand the frequency of 21 in 716639.

Advancing to step 1:
The number 21 fits into 7 0 times, leaving a remainder of 7.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 7 after subtracting 0 from 7.
Grab the next digit (1) from the dividend, add it to 7, then carry on: 71 / 21

Moving on to step 2:
21 can be fit into 71 3 times, resulting in a remainder of 8.
The next digit of our result is 3. 
Result so far: 3.0
Subtracting 63 from 71 leaves us with 8.
Grab the next digit (6) from the dividend, add it to 8, then carry on: 86 / 21

Moving on to step 3:
If we divide 86 by 21, we get 4 and a remainder of 2.
The number 4 becomes the next digit in our result. 
Result so far: 34.0
If we subtract 84 from 86, we get 2.
Bring next digit (6) of the dividend behind the 2 and repeat the process: 26 / 21

Going ahead to step 4:
21 can be fit into 26 1 times, resulting in a remainder of 5.
Record the quotient 1 as the next digit in the result. 
Result so far: 341.0
If we take 21 away from 26, we end up with 5.
Include the next digit (3) from the dividend after 5, then repeat: 53 / 21

Moving on to step 5:
The number 21 fits into 53 2 times, leaving a remainder of 11.
Put 2 as the next digit of the answer. 
Result so far: 3412.0
Deduct 42 from 53 and we're left with 11.
Take the next digit (9) from the dividend and append it to 11, then repeat: 119 / 21

Advancing to step 6:
If we divide 119 by 21, we get 5 and a remainder of 14.
The number 5 becomes the next digit in our result. 
Result so far: 34125.0
The remainder is 14 after subtracting 105 from 119.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Step 7:
When dividing 140 by 21, we get 6 with a remainder of 14.
Put 6 as the next digit of the answer. 
Result so far: 34125.6
The remainder is 14 after subtracting 126 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Moving on to step 8:
21 can be fit into 140 6 times, resulting in a remainder of 14.
Put 6 as the next digit of the answer. 
Result so far: 34125.66
Subtracting 126 from 140 leaves us with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

In conclusion, the division gives 34125.66 with a balance of 0.014.