642991 ÷ 16 
The aim is to understand the frequency of 16 in 642991.

Advancing to step 1:
6 divided by 16 is 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 16

Going ahead to step 2:
The number 16 fits into 64 4 times, leaving a remainder of 0.
Use 4 as the next digit of our solution. 
Result so far: 4.0
Subtracting 64 from 64 leaves us with 0.
Grab the next digit (2) from the dividend, add it to 0, then carry on: 2 / 16

On to step 3:
16 goes into 2 0 times with a remainder of 2.
Record the quotient 0 as the next digit in the result. 
Result so far: 40.0
Subtracting 0 from 2 leaves us with 2.
Take the next digit (9) from the dividend and append it to 2, then repeat: 29 / 16

Going ahead to step 4:
16 can be fit into 29 1 times, resulting in a remainder of 13.
Record the quotient 1 as the next digit in the result. 
Result so far: 401.0
The remainder is 13 after subtracting 16 from 29.
Grab the next digit (9) from the dividend, add it to 13, then carry on: 139 / 16

Advancing to step 5:
16 goes into 139 8 times with a remainder of 11.
The number 8 becomes the next digit in our result. 
Result so far: 4018.0
Subtracting 128 from 139 leaves us with 11.
Grab the next digit (1) from the dividend, add it to 11, then carry on: 111 / 16

On to step 6:
If we divide 111 by 16, we get 6 and a remainder of 15.
The number 6 becomes the next digit in our result. 
Result so far: 40186.0
If we take 96 away from 111, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 7:
16 can be fit into 150 9 times, resulting in a remainder of 6.
The number 9 becomes the next digit in our result. 
Result so far: 40186.9
If we take 144 away from 150, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 8:
16 goes into 60 3 times with a remainder of 12.
Record the quotient 3 as the next digit in the result. 
Result so far: 40186.93
The remainder is 12 after subtracting 48 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Let's proceed to step 9:
When dividing 120 by 16, we get 7 with a remainder of 8.
Put 7 as the next digit of the answer. 
Result so far: 40186.937
If we take 112 away from 120, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 10:
When dividing 80 by 16, we get 5 with a remainder of 0.
The next digit of our result is 5. 
Result so far: 40186.9375
If we take 80 away from 80, 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 11:
When dividing 0 by 16, we get 0 with a remainder of 0.
The next digit of our result is 0. 
Result so far: 40186.9375
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 12:
0 divided by 16 is 0 with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 40186.9375
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.

After the division, we end up with 40186.9375 and a remainder of 0.0.