Write the following Hindu-Arabic numeral for the following Roman numeral:

$\mathrm{DXCVII}$

Write the following Hindu-Arabic numeral for the following Roman numeral:

$\mathrm{DCLXXV}$

Write the following Hindu-Arabic numeral for the following Roman numeral:

$\mathrm{DCCCLXXXVIII}$

Write the following Hindu-Arabic numeral for the following Roman numeral:

$\mathrm{MDXXXIV}$

A mobile number consist of nine digits. The first four digits of the number are $9, 9, 9 \text{and} 7$ and the last three digits are $3, 5 \text{and} 6$. The remaining digits are different. Frame the greatest possible number using the remaining digits.

In a four-digit number, digit at the tens place is $4$, digit at the ones place is two-fourth of the tens place digits, digit at the hundred place is $0$ and the digit at the thousands place is double the digit at the tens place. Determine the number.

Determine the difference between the greatest $7$-digit number with four equal digits and the smallest $6$-digit number with three different digits.

The product of face value and face value of digit $6$ in the number $4,56,702$ is _____.

The relation between $1$ million $=$_____ hundred thousand.