256515 divided by 21 
The aim is to understand the frequency of 21 in 256515.

Let's proceed to step 1:
The number 21 fits into 2 0 times, leaving a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 2 leaves us with 2.
Bring next digit (5) of the dividend behind the 2 and repeat the process: 25 / 21

On to step 2:
If we divide 25 by 21, we get 1 and a remainder of 4.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we subtract 21 from 25, we get 4.
Take the next digit (6) from the dividend and append it to 4, then repeat: 46 / 21

Advancing to step 3:
46 divided by 21 is 2 with a remainder of 4.
Write down 2 as next digit of the result. 
Result so far: 12.0
The remainder is 4 after subtracting 42 from 46.
Take the next digit (5) from the dividend and append it to 4, then repeat: 45 / 21

Going ahead to step 4:
When dividing 45 by 21, we get 2 with a remainder of 3.
Put 2 as the next digit of the answer. 
Result so far: 122.0
If we subtract 42 from 45, we get 3.
Fetch the next digit (1) from the dividend, attach it to 3 and continue: 31 / 21

Advancing to step 5:
21 can be fit into 31 1 times, resulting in a remainder of 10.
Put 1 as the next digit of the answer. 
Result so far: 1221.0
Deduct 21 from 31 and we're left with 10.
Fetch the next digit (5) from the dividend, attach it to 10 and continue: 105 / 21

Let's proceed to step 6:
The number 21 fits into 105 5 times, leaving a remainder of 0.
Use 5 as the next digit of our solution. 
Result so far: 12215.0
Deduct 105 from 105 and we're left 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.

Advancing to step 7:
When dividing 0 by 21, we get 0 with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 12215.0
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.

Step 8:
21 goes into 0 0 times with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 12215.0
Deduct 0 from 0 and we're left 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.

The quotient of the division is 12215.0, and the remainder is 0.0.