We're dividing 513854 by 21 
The aim is to understand the frequency of 21 in 513854.

Going ahead to step 1:
5 divided by 21 is 0 with a remainder of 5.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Fetch the next digit (1) from the dividend, attach it to 5 and continue: 51 / 21

Advancing to step 2:
The number 21 fits into 51 2 times, leaving a remainder of 9.
The next digit of our result is 2. 
Result so far: 2.0
If we subtract 42 from 51, we get 9.
Grab the next digit (3) from the dividend, add it to 9, then carry on: 93 / 21

Step 3:
21 goes into 93 4 times with a remainder of 9.
Record the quotient 4 as the next digit in the result. 
Result so far: 24.0
Deduct 84 from 93 and we're left with 9.
Grab the next digit (8) from the dividend, add it to 9, then carry on: 98 / 21

Moving on to step 4:
The number 21 fits into 98 4 times, leaving a remainder of 14.
The number 4 becomes the next digit in our result. 
Result so far: 244.0
Deduct 84 from 98 and we're left with 14.
Fetch the next digit (5) from the dividend, attach it to 14 and continue: 145 / 21

Let's proceed to step 5:
21 goes into 145 6 times with a remainder of 19.
Write down 6 as next digit of the result. 
Result so far: 2446.0
Subtracting 126 from 145 leaves us with 19.
Fetch the next digit (4) from the dividend, attach it to 19 and continue: 194 / 21

On to step 6:
21 goes into 194 9 times with a remainder of 5.
Put 9 as the next digit of the answer. 
Result so far: 24469.0
If we subtract 189 from 194, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Step 7:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 24469.2
If we take 42 away from 50, we end up 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.

Step 8:
80 divided by 21 is 3 with a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 24469.23
If we subtract 63 from 80, we 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.

Moving on to step 9:
21 goes into 170 8 times with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 24469.238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 10:
When dividing 20 by 21, we get 0 with a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 24469.238
Deduct 0 from 20 and we're left with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 11:
21 can be fit into 200 9 times, resulting in a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 24469.23809
Deduct 189 from 200 and we're left 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 12:
When dividing 110 by 21, we get 5 with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 24469.238095
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 13:
21 goes into 50 2 times with a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 24469.2380952
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.

Advancing to step 14:
The number 21 fits into 80 3 times, leaving a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 24469.23809523
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.

The quotient of the division is 24469.23809523, and the remainder is 1.7e-08.