We divide 19913921 by 643
The aim is to understand the frequency of 643 in 19913921.

On to step 1:
643 goes into 1 0 times with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 1, we get 1.
Grab the next digit (9) from the dividend, add it to 1, then carry on: 19 / 643

Moving on to step 2:
19 divided by 643 is 0 with a remainder of 19.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 19 to get 19.
Grab the next digit (9) from the dividend, add it to 19, then carry on: 199 / 643

Advancing to step 3:
When dividing 199 by 643, we get 0 with a remainder of 199.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 199 to get 199.
Bring next digit (1) of the dividend behind the 199 and repeat the process: 1991 / 643

On to step 4:
643 goes into 1991 3 times with a remainder of 62.
Use 3 as the next digit of our solution. 
Result so far: 3.0
The remainder is 62 after subtracting 1929 from 1991.
Grab the next digit (3) from the dividend, add it to 62, then carry on: 623 / 643

Going ahead to step 5:
If we divide 623 by 643, we get 0 and a remainder of 623.
The number 0 becomes the next digit in our result. 
Result so far: 30.0
Deduct 0 from 623 and we're left with 623.
Include the next digit (9) from the dividend after 623, then repeat: 6239 / 643

Going ahead to step 6:
The number 643 fits into 6239 9 times, leaving a remainder of 452.
The number 9 becomes the next digit in our result. 
Result so far: 309.0
The remainder is 452 after subtracting 5787 from 6239.
Include the next digit (2) from the dividend after 452, then repeat: 4522 / 643

Step 7:
643 goes into 4522 7 times with a remainder of 21.
Record the quotient 7 as the next digit in the result. 
Result so far: 3097.0
The remainder is 21 after subtracting 4501 from 4522.
Bring next digit (1) of the dividend behind the 21 and repeat the process: 211 / 643

Step 8:
643 goes into 211 0 times with a remainder of 211.
Put 0 as the next digit of the answer. 
Result so far: 30970.0
Subtract 0 from 211 to get 211.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2110, and continue the process.

Step 9:
643 goes into 2110 3 times with a remainder of 181.
The next digit of our result is 3. 
Result so far: 30970.3
If we subtract 1929 from 2110, we get 181.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1810, and continue the process.

Moving on to step 10:
When dividing 1810 by 643, we get 2 with a remainder of 524.
Use 2 as the next digit of our solution. 
Result so far: 30970.32
Subtracting 1286 from 1810 leaves us with 524.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5240, and continue the process.

Moving on to step 11:
643 goes into 5240 8 times with a remainder of 96.
The next digit of our result is 8. 
Result so far: 30970.328
If we subtract 5144 from 5240, we get 96.
Since there are no more digits in the dividend, we add a zero to the remainder making it 960, and continue the process.

On to step 12:
643 can be fit into 960 1 times, resulting in a remainder of 317.
Write down 1 as next digit of the result. 
Result so far: 30970.3281
Subtract 643 from 960 to get 317.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3170, and continue the process.

Going ahead to step 13:
The number 643 fits into 3170 4 times, leaving a remainder of 598.
Put 4 as the next digit of the answer. 
Result so far: 30970.32814
The remainder is 598 after subtracting 2572 from 3170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5980, and continue the process.

Going ahead to step 14:
5980 divided by 643 is 9 with a remainder of 193.
Put 9 as the next digit of the answer. 
Result so far: 30970.328149
If we subtract 5787 from 5980, we get 193.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1930, and continue the process.

Moving on to step 15:
643 can be fit into 1930 3 times, resulting in a remainder of 1.
The next digit of our result is 3. 
Result so far: 30970.3281493
Subtracting 1929 from 1930 leaves us 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.

Going ahead to step 16:
643 goes into 10 0 times with a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 30970.3281493
If we subtract 0 from 10, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

In conclusion, the division gives 30970.3281493 with a balance of 1e-08.