379436 divided by 21 
The aim is to understand the frequency of 21 in 379436.

Moving on to step 1:
21 goes into 3 0 times with a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Fetch the next digit (7) from the dividend, attach it to 3 and continue: 37 / 21

Advancing to step 2:
21 can be fit into 37 1 times, resulting in a remainder of 16.
The next digit of our result is 1. 
Result so far: 1.0
If we take 21 away from 37, we end up with 16.
Take the next digit (9) from the dividend and append it to 16, then repeat: 169 / 21

Advancing to step 3:
169 divided by 21 is 8 with a remainder of 1.
Put 8 as the next digit of the answer. 
Result so far: 18.0
Deduct 168 from 169 and we're left with 1.
Fetch the next digit (4) from the dividend, attach it to 1 and continue: 14 / 21

Moving on to step 4:
14 divided by 21 is 0 with a remainder of 14.
The number 0 becomes the next digit in our result. 
Result so far: 180.0
The remainder is 14 after subtracting 0 from 14.
Take the next digit (3) from the dividend and append it to 14, then repeat: 143 / 21

On to step 5:
143 divided by 21 is 6 with a remainder of 17.
Put 6 as the next digit of the answer. 
Result so far: 1806.0
Subtracting 126 from 143 leaves us with 17.
Append the next digit (6) from the dividend to 17 and continue with: 176 / 21

Going ahead to step 6:
If we divide 176 by 21, we get 8 and a remainder of 8.
Write down 8 as next digit of the result. 
Result so far: 18068.0
The remainder is 8 after subtracting 168 from 176.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Step 7:
80 divided by 21 is 3 with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 18068.3
Subtracting 63 from 80 leaves us 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.

On to step 8:
170 divided by 21 is 8 with a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 18068.38
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.

Moving on to step 9:
21 can be fit into 20 0 times, resulting in a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 18068.38
The remainder is 20 after subtracting 0 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

On to step 10:
21 goes into 200 9 times with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 18068.3809
Subtract 189 from 200 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Advancing to step 11:
21 can be fit into 110 5 times, resulting in a remainder of 5.
The next digit of our result is 5. 
Result so far: 18068.38095
Subtracting 105 from 110 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 12:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 18068.380952
If we take 42 away from 50, 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.

Advancing to step 13:
21 can be fit into 80 3 times, resulting in a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 18068.3809523
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:
When dividing 170 by 21, we get 8 with a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 18068.38095238
Subtracting 168 from 170 leaves us 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 final outcome is 18068.38095238, with a leftover of 2e-09.