643639 divided by 2 
The aim is to understand the frequency of 2 in 643639.

Step 1:
When dividing 6 by 2, we get 3 with a remainder of 0.
The next digit of our result is 3. 
Result so far: 3.0
If we take 6 away from 6, we end up with 0.
Fetch the next digit (4) from the dividend, attach it to 0 and continue: 4 / 2

Going ahead to step 2:
2 can be fit into 4 2 times, resulting in a remainder of 0.
Put 2 as the next digit of the answer. 
Result so far: 32.0
If we subtract 4 from 4, we get 0.
Take the next digit (3) from the dividend and append it to 0, then repeat: 3 / 2

Going ahead to step 3:
2 goes into 3 1 times with a remainder of 1.
The next digit of our result is 1. 
Result so far: 321.0
Deduct 2 from 3 and we're left with 1.
Take the next digit (6) from the dividend and append it to 1, then repeat: 16 / 2

On to step 4:
If we divide 16 by 2, we get 8 and a remainder of 0.
The number 8 becomes the next digit in our result. 
Result so far: 3218.0
Deduct 16 from 16 and we're left with 0.
Bring next digit (3) of the dividend behind the 0 and repeat the process: 3 / 2

Advancing to step 5:
2 goes into 3 1 times with a remainder of 1.
The next digit of our result is 1. 
Result so far: 32181.0
The remainder is 1 after subtracting 2 from 3.
Bring next digit (9) of the dividend behind the 1 and repeat the process: 19 / 2

Moving on to step 6:
The number 2 fits into 19 9 times, leaving a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 321819.0
Deduct 18 from 19 and we're left with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

On to step 7:
If we divide 10 by 2, we get 5 and a remainder of 0.
Record the quotient 5 as the next digit in the result. 
Result so far: 321819.5
The remainder is 0 after subtracting 10 from 10.
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 8:
The number 2 fits into 0 0 times, leaving a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 321819.5
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.

On to step 9:
If we divide 0 by 2, we get 0 and a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 321819.5
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.

Our division results in 321819.5 with a remaining 0.0.