501329 ÷ 21 
The aim is to understand the frequency of 21 in 501329.

Let's proceed to step 1:
When dividing 5 by 21, we get 0 with a remainder of 5.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 5 after subtracting 0 from 5.
Include the next digit (0) from the dividend after 5, then repeat: 50 / 21

Step 2:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 2.0
The remainder is 8 after subtracting 42 from 50.
Take the next digit (1) from the dividend and append it to 8, then repeat: 81 / 21

Moving on to step 3:
21 can be fit into 81 3 times, resulting in a remainder of 18.
The number 3 becomes the next digit in our result. 
Result so far: 23.0
If we take 63 away from 81, we end up with 18.
Append the next digit (3) from the dividend to 18 and continue with: 183 / 21

Moving on to step 4:
21 can be fit into 183 8 times, resulting in a remainder of 15.
Record the quotient 8 as the next digit in the result. 
Result so far: 238.0
Deduct 168 from 183 and we're left with 15.
Grab the next digit (2) from the dividend, add it to 15, then carry on: 152 / 21

Step 5:
If we divide 152 by 21, we get 7 and a remainder of 5.
Record the quotient 7 as the next digit in the result. 
Result so far: 2387.0
If we take 147 away from 152, we end up with 5.
Grab the next digit (9) from the dividend, add it to 5, then carry on: 59 / 21

Let's proceed to step 6:
When dividing 59 by 21, we get 2 with a remainder of 17.
The number 2 becomes the next digit in our result. 
Result so far: 23872.0
Subtract 42 from 59 to get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Let's proceed to step 7:
When dividing 170 by 21, we get 8 with a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 23872.8
Subtracting 168 from 170 leaves us with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 8:
20 divided by 21 is 0 with a remainder of 20.
The next digit of our result is 0. 
Result so far: 23872.8
The remainder is 20 after subtracting 0 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Advancing to step 9:
When dividing 200 by 21, we get 9 with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 23872.809
Subtracting 189 from 200 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 10:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 23872.8095
Subtracting 105 from 110 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 11:
If we divide 50 by 21, we get 2 and a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 23872.80952
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 12:
If we divide 80 by 21, we get 3 and a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 23872.809523
The remainder is 17 after subtracting 63 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Moving on to step 13:
If we divide 170 by 21, we get 8 and a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 23872.8095238
If we subtract 168 from 170, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 14:
21 can be fit into 20 0 times, resulting in a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 23872.8095238
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

In conclusion, the division gives 23872.8095238 with a balance of 2e-08.