378995 divided by 21 
The aim is to understand the frequency of 21 in 378995.

On to step 1:
If we divide 3 by 21, we get 0 and a remainder of 3.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 3, we get 3.
Fetch the next digit (7) from the dividend, attach it to 3 and continue: 37 / 21

On to step 2:
When dividing 37 by 21, we get 1 with a remainder of 16.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
The remainder is 16 after subtracting 21 from 37.
Bring next digit (8) of the dividend behind the 16 and repeat the process: 168 / 21

Let's proceed to step 3:
If we divide 168 by 21, we get 8 and a remainder of 0.
The number 8 becomes the next digit in our result. 
Result so far: 18.0
Subtract 168 from 168 to get 0.
Bring next digit (9) of the dividend behind the 0 and repeat the process: 9 / 21

Going ahead to step 4:
9 divided by 21 is 0 with a remainder of 9.
The next digit of our result is 0. 
Result so far: 180.0
Deduct 0 from 9 and we're left with 9.
Include the next digit (9) from the dividend after 9, then repeat: 99 / 21

Advancing to step 5:
If we divide 99 by 21, we get 4 and a remainder of 15.
Put 4 as the next digit of the answer. 
Result so far: 1804.0
Subtract 84 from 99 to get 15.
Grab the next digit (5) from the dividend, add it to 15, then carry on: 155 / 21

Going ahead to step 6:
21 goes into 155 7 times with a remainder of 8.
Record the quotient 7 as the next digit in the result. 
Result so far: 18047.0
Deduct 147 from 155 and we're left 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 7:
When dividing 80 by 21, we get 3 with a remainder of 17.
Record the quotient 3 as the next digit in the result. 
Result so far: 18047.3
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Step 8:
When dividing 170 by 21, we get 8 with a remainder of 2.
The next digit of our result is 8. 
Result so far: 18047.38
Deduct 168 from 170 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 9:
20 divided by 21 is 0 with a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 18047.38
If we subtract 0 from 20, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Let's proceed to step 10:
200 divided by 21 is 9 with a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 18047.3809
If we take 189 away from 200, we end up with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 11:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 18047.38095
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Let's proceed to step 12:
When dividing 50 by 21, we get 2 with a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 18047.380952
Deduct 42 from 50 and we're left 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.

Let's proceed to step 13:
When dividing 80 by 21, we get 3 with a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 18047.3809523
If we subtract 63 from 80, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Let's proceed to step 14:
If we divide 170 by 21, we get 8 and a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 18047.38095238
If we take 168 away from 170, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

The quotient of the division is 18047.38095238, and the remainder is 2e-09.