In the Roman numeral system, 'X' can be subtracted from L and C only. (L= 50) and (C = 100) For example:

XL = 50 - 10 = 40 
XC = 100 -10 = 90
We can not write XD or XM.

The given options of odd numbers are: 3, 5, 7, 9.
Here 3, 5 and 7 are prime numbers.

So, 9 is the smallest odd composite number.
 

 The successor of a number is the number that comes right after it.

Thus, the successor of 101099 is
101099 + 1 = 101100.

1 million = 1,000,000

The successor of a number is one more than that number and the predecessor of a number is one less than that number.

The successor of 1,000,000 = 1000000 + 1 = 1000001
The predecessor of 1,000,000 = 1000000 - 1 = 999999

The difference between the successor and the predecessor of 1,000,000 = 1000001 - 999999 = 2.
In fact the difference between the successor and predecessor of any number will always be 2 !! Try it yourself

CM = 900

XL = 40 

V = 5

CM     XL    V 
900 + 40 + 5 = 945

Therefore CMXLV = 945.

1 crore $=1,00,00,000$
Number of tens in 1 crore
$=\frac{10000000}{10}=1000000$

$\therefore 1000000$ tens make 1 crore.

To round off a number to its nearest thousand we check the last three digits of the number i.e. the digits at the hundreds place, tens place and ones place. In case the number formed by these is 500 or above, we round up the number to the higher value and in case the number is less than 500, we round it down to the lower value.

The given number is 58195. Our options are 58000 and 59000. The last three digits of 58195 are 195.
195 < 500.

Therefore 58195 when rounding off to the nearest thousand is 58000.
 

$\begin{array}{ccccccc}I& V& X& L& C& D& M\\ 1& 5& 10& 50& 100& 500& 1000\end{array}$
There are the 7 basic symbols in Roman numerals.

Place values of 6 in 438269160 are  $6\times 10000=60000$ and $6\times 10=60$.

The product of the place values of 6 in 438269160 divided by 1000$=\frac{60000\times 60}{1000}=\frac{3600000}{1000}=3600$

2499 = 2000 + 400 + 90  + 9
         =   MM + CD  + XC + IX
         = MMCDXCIX

($\because$ 2000 = MM, 400 = CD, 90 = XC, 9 = IX)