21872900 ÷ 19 
The aim is to understand the frequency of 19 in 21872900.

On to step 1:
When dividing 2 by 19, we get 0 with a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Grab the next digit (1) from the dividend, add it to 2, then carry on: 21 / 19

On to step 2:
When dividing 21 by 19, we get 1 with a remainder of 2.
Put 1 as the next digit of the answer. 
Result so far: 1.0
Deduct 19 from 21 and we're left with 2.
Take the next digit (8) from the dividend and append it to 2, then repeat: 28 / 19

Advancing to step 3:
When dividing 28 by 19, we get 1 with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 11.0
Deduct 19 from 28 and we're left with 9.
Grab the next digit (7) from the dividend, add it to 9, then carry on: 97 / 19

Moving on to step 4:
97 divided by 19 is 5 with a remainder of 2.
Record the quotient 5 as the next digit in the result. 
Result so far: 115.0
The remainder is 2 after subtracting 95 from 97.
Fetch the next digit (2) from the dividend, attach it to 2 and continue: 22 / 19

Let's proceed to step 5:
When dividing 22 by 19, we get 1 with a remainder of 3.
Record the quotient 1 as the next digit in the result. 
Result so far: 1151.0
The remainder is 3 after subtracting 19 from 22.
Take the next digit (9) from the dividend and append it to 3, then repeat: 39 / 19

Advancing to step 6:
When dividing 39 by 19, we get 2 with a remainder of 1.
Use 2 as the next digit of our solution. 
Result so far: 11512.0
If we take 38 away from 39, we end up with 1.
Include the next digit (0) from the dividend after 1, then repeat: 10 / 19

Step 7:
19 can be fit into 10 0 times, resulting in a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 115120.0
If we take 0 away from 10, we end up with 10.
Append the next digit (0) from the dividend to 10 and continue with: 100 / 19

On to step 8:
When dividing 100 by 19, we get 5 with a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 1151205.0
Subtract 95 from 100 to 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.

Going ahead to step 9:
If we divide 50 by 19, we get 2 and a remainder of 12.
The next digit of our result is 2. 
Result so far: 1151205.2
Deduct 38 from 50 and we're left 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.

Going ahead to step 10:
120 divided by 19 is 6 with a remainder of 6.
Use 6 as the next digit of our solution. 
Result so far: 1151205.26
If we subtract 114 from 120, we 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.

Let's proceed to step 11:
19 can be fit into 60 3 times, resulting in a remainder of 3.
The next digit of our result is 3. 
Result so far: 1151205.263
Deduct 57 from 60 and we're left with 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 12:
19 goes into 30 1 times with a remainder of 11.
The next digit of our result is 1. 
Result so far: 1151205.2631
If we take 19 away from 30, we end up 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.

Let's proceed to step 13:
110 divided by 19 is 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 1151205.26315
The remainder is 15 after subtracting 95 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 14:
When dividing 150 by 19, we get 7 with a remainder of 17.
Record the quotient 7 as the next digit in the result. 
Result so far: 1151205.263157
Subtracting 133 from 150 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

On to step 15:
19 goes into 170 8 times with a remainder of 18.
Record the quotient 8 as the next digit in the result. 
Result so far: 1151205.2631578
The remainder is 18 after subtracting 152 from 170.
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 16:
19 goes into 180 9 times with a remainder of 9.
Put 9 as the next digit of the answer. 
Result so far: 1151205.26315789
Subtracting 171 from 180 leaves us with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

The final result is 1151205.26315789 with a remainder of 9e-09.