We look at the division of 699571 by 21 
The aim is to understand the frequency of 21 in 699571.

Going ahead to step 1:
The number 21 fits into 6 0 times, leaving a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 6, we get 6.
Fetch the next digit (9) from the dividend, attach it to 6 and continue: 69 / 21

Let's proceed to step 2:
When dividing 69 by 21, we get 3 with a remainder of 6.
Put 3 as the next digit of the answer. 
Result so far: 3.0
If we subtract 63 from 69, we get 6.
Grab the next digit (9) from the dividend, add it to 6, then carry on: 69 / 21

Step 3:
If we divide 69 by 21, we get 3 and a remainder of 6.
Put 3 as the next digit of the answer. 
Result so far: 33.0
Deduct 63 from 69 and we're left with 6.
Grab the next digit (5) from the dividend, add it to 6, then carry on: 65 / 21

Moving on to step 4:
The number 21 fits into 65 3 times, leaving a remainder of 2.
The number 3 becomes the next digit in our result. 
Result so far: 333.0
Subtract 63 from 65 to get 2.
Bring next digit (7) of the dividend behind the 2 and repeat the process: 27 / 21

Moving on to step 5:
If we divide 27 by 21, we get 1 and a remainder of 6.
Record the quotient 1 as the next digit in the result. 
Result so far: 3331.0
The remainder is 6 after subtracting 21 from 27.
Grab the next digit (1) from the dividend, add it to 6, then carry on: 61 / 21

On to step 6:
When dividing 61 by 21, we get 2 with a remainder of 19.
The next digit of our result is 2. 
Result so far: 33312.0
Deduct 42 from 61 and we're left with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Going ahead to step 7:
190 divided by 21 is 9 with a remainder of 1.
Write down 9 as next digit of the result. 
Result so far: 33312.9
If we take 189 away from 190, we end up 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.

On to step 8:
21 can be fit into 10 0 times, resulting in a remainder of 10.
Write down 0 as next digit of the result. 
Result so far: 33312.9
If we take 0 away from 10, we end up with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Going ahead to step 9:
21 can be fit into 100 4 times, resulting in a remainder of 16.
The number 4 becomes the next digit in our result. 
Result so far: 33312.904
The remainder is 16 after subtracting 84 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 10:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 33312.9047
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 11:
21 can be fit into 130 6 times, resulting in a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 33312.90476
Deduct 126 from 130 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Going ahead to step 12:
21 goes into 40 1 times with a remainder of 19.
Write down 1 as next digit of the result. 
Result so far: 33312.904761
If we subtract 21 from 40, we get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

On to step 13:
When dividing 190 by 21, we get 9 with a remainder of 1.
The next digit of our result is 9. 
Result so far: 33312.9047619
Deduct 189 from 190 and we're left 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.

Let's proceed to step 14:
If we divide 10 by 21, we get 0 and a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 33312.9047619
Deduct 0 from 10 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

The final outcome is 33312.9047619, with a leftover of 1e-08.