The population of China in $2001$ was $1276300000$ and in $2005$ it was $1307600000$. What was the increase in population? Write it in words.

Find the difference of the smallest and greatest five-digit numbers formed by the digits $6, 3, 8, 4$ using only one of these digits twice.

Find the number formed by interchanging the digits $5$ and $7$ in $586701$. Also find the difference between the numbers.

Write $10$ million in the Indian system of numeration.