We look at the division of 18498228 by 21 
The aim is to understand the frequency of 21 in 18498228.

Advancing to step 1:
When dividing 1 by 21, we get 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Append the next digit (8) from the dividend to 1 and continue with: 18 / 21

Let's proceed to step 2:
21 can be fit into 18 0 times, resulting in a remainder of 18.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 18 after subtracting 0 from 18.
Grab the next digit (4) from the dividend, add it to 18, then carry on: 184 / 21

Advancing to step 3:
The number 21 fits into 184 8 times, leaving a remainder of 16.
The next digit of our result is 8. 
Result so far: 8.0
The remainder is 16 after subtracting 168 from 184.
Grab the next digit (9) from the dividend, add it to 16, then carry on: 169 / 21

On to step 4:
If we divide 169 by 21, we get 8 and a remainder of 1.
Record the quotient 8 as the next digit in the result. 
Result so far: 88.0
Subtract 168 from 169 to get 1.
Take the next digit (8) from the dividend and append it to 1, then repeat: 18 / 21

Advancing to step 5:
If we divide 18 by 21, we get 0 and a remainder of 18.
Record the quotient 0 as the next digit in the result. 
Result so far: 880.0
If we take 0 away from 18, we end up with 18.
Bring next digit (2) of the dividend behind the 18 and repeat the process: 182 / 21

Let's proceed to step 6:
If we divide 182 by 21, we get 8 and a remainder of 14.
The number 8 becomes the next digit in our result. 
Result so far: 8808.0
Subtract 168 from 182 to get 14.
Take the next digit (2) from the dividend and append it to 14, then repeat: 142 / 21

Let's proceed to step 7:
21 can be fit into 142 6 times, resulting in a remainder of 16.
Record the quotient 6 as the next digit in the result. 
Result so far: 88086.0
If we take 126 away from 142, we end up with 16.
Bring next digit (8) of the dividend behind the 16 and repeat the process: 168 / 21

On to step 8:
When dividing 168 by 21, we get 8 with a remainder of 0.
Record the quotient 8 as the next digit in the result. 
Result so far: 880868.0
If we take 168 away from 168, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Moving on to step 9:
The number 21 fits into 0 0 times, leaving a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 880868.0
Subtracting 0 from 0 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Let's proceed to step 10:
0 divided by 21 is 0 with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 880868.0
Subtracting 0 from 0 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

After the division, we end up with 880868.0 and a remainder of 0.0.