We look at the division of 34357782 by 21 
The aim is to understand the frequency of 21 in 34357782.

Moving on to step 1:
3 divided by 21 is 0 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 (4) from the dividend, attach it to 3 and continue: 34 / 21

Advancing to step 2:
The number 21 fits into 34 1 times, leaving a remainder of 13.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 21 away from 34, we end up with 13.
Grab the next digit (3) from the dividend, add it to 13, then carry on: 133 / 21

Going ahead to step 3:
When dividing 133 by 21, we get 6 with a remainder of 7.
Use 6 as the next digit of our solution. 
Result so far: 16.0
Subtract 126 from 133 to get 7.
Grab the next digit (5) from the dividend, add it to 7, then carry on: 75 / 21

Let's proceed to step 4:
75 divided by 21 is 3 with a remainder of 12.
Put 3 as the next digit of the answer. 
Result so far: 163.0
The remainder is 12 after subtracting 63 from 75.
Bring next digit (7) of the dividend behind the 12 and repeat the process: 127 / 21

Let's proceed to step 5:
When dividing 127 by 21, we get 6 with a remainder of 1.
The number 6 becomes the next digit in our result. 
Result so far: 1636.0
Deduct 126 from 127 and we're left with 1.
Fetch the next digit (7) from the dividend, attach it to 1 and continue: 17 / 21

Advancing to step 6:
The number 21 fits into 17 0 times, leaving a remainder of 17.
Use 0 as the next digit of our solution. 
Result so far: 16360.0
Subtract 0 from 17 to get 17.
Grab the next digit (8) from the dividend, add it to 17, then carry on: 178 / 21

Going ahead to step 7:
21 goes into 178 8 times with a remainder of 10.
Record the quotient 8 as the next digit in the result. 
Result so far: 163608.0
The remainder is 10 after subtracting 168 from 178.
Bring next digit (2) of the dividend behind the 10 and repeat the process: 102 / 21

Step 8:
When dividing 102 by 21, we get 4 with a remainder of 18.
Write down 4 as next digit of the result. 
Result so far: 1636084.0
If we take 84 away from 102, we end up with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Advancing to step 9:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 1636084.8
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 10:
If we divide 120 by 21, we get 5 and a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 1636084.85
Subtract 105 from 120 to get 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 11:
150 divided by 21 is 7 with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 1636084.857
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 12:
21 goes into 30 1 times with a remainder of 9.
The next digit of our result is 1. 
Result so far: 1636084.8571
Subtracting 21 from 30 leaves us with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 13:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 1636084.85714
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Going ahead to step 14:
60 divided by 21 is 2 with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 1636084.857142
If we subtract 42 from 60, we get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Advancing to step 15:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 1636084.8571428
Subtract 168 from 180 to get 12.
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 16:
When dividing 120 by 21, we get 5 with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 1636084.85714285
If we subtract 105 from 120, we get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

The quotient of the division is 1636084.85714285, and the remainder is 1.5e-08.