21430521 ÷ 900 
The aim is to understand the frequency of 900 in 21430521.

Step 1:
900 can be fit into 2 0 times, resulting in a remainder of 2.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 2 after subtracting 0 from 2.
Append the next digit (1) from the dividend to 2 and continue with: 21 / 900

Let's proceed to step 2:
If we divide 21 by 900, we get 0 and a remainder of 21.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 21 after subtracting 0 from 21.
Fetch the next digit (4) from the dividend, attach it to 21 and continue: 214 / 900

On to step 3:
900 goes into 214 0 times with a remainder of 214.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 214, we get 214.
Grab the next digit (3) from the dividend, add it to 214, then carry on: 2143 / 900

Step 4:
The number 900 fits into 2143 2 times, leaving a remainder of 343.
The next digit of our result is 2. 
Result so far: 2.0
Subtract 1800 from 2143 to get 343.
Grab the next digit (0) from the dividend, add it to 343, then carry on: 3430 / 900

Let's proceed to step 5:
If we divide 3430 by 900, we get 3 and a remainder of 730.
The number 3 becomes the next digit in our result. 
Result so far: 23.0
If we subtract 2700 from 3430, we get 730.
Append the next digit (5) from the dividend to 730 and continue with: 7305 / 900

Moving on to step 6:
If we divide 7305 by 900, we get 8 and a remainder of 105.
Use 8 as the next digit of our solution. 
Result so far: 238.0
If we subtract 7200 from 7305, we get 105.
Take the next digit (2) from the dividend and append it to 105, then repeat: 1052 / 900

Moving on to step 7:
If we divide 1052 by 900, we get 1 and a remainder of 152.
The next digit of our result is 1. 
Result so far: 2381.0
If we take 900 away from 1052, we end up with 152.
Append the next digit (1) from the dividend to 152 and continue with: 1521 / 900

On to step 8:
The number 900 fits into 1521 1 times, leaving a remainder of 621.
The number 1 becomes the next digit in our result. 
Result so far: 23811.0
Deduct 900 from 1521 and we're left with 621.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6210, and continue the process.

On to step 9:
When dividing 6210 by 900, we get 6 with a remainder of 810.
Write down 6 as next digit of the result. 
Result so far: 23811.6
If we take 5400 away from 6210, we end up with 810.
Since there are no more digits in the dividend, we add a zero to the remainder making it 8100, and continue the process.

Advancing to step 10:
900 can be fit into 8100 9 times, resulting in a remainder of 0.
Put 9 as the next digit of the answer. 
Result so far: 23811.69
If we subtract 8100 from 8100, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 11:
900 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 23811.69
If we take 0 away from 0, 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.

On to step 12:
When dividing 0 by 900, we get 0 with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 23811.69
Subtract 0 from 0 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

In conclusion, the division gives 23811.69 with a balance of 0.0.