How many $6$-digit numbers are there in all?

Mention the greatest $5$-digit number having four different digits.

Determine the greatest and smallest numbers in the following:

$8,12,293; 62,172; 55,123; 42,13,186; 11,12,192$

Determine the greatest and smallest numbers in the following:

$9,21,393; 8,13,593; 4,21,391; 9,99,911; 6,21,302$

Determine the greatest and smallest numbers in the following:

$1,30,135; 1,31,301; 1,31,429; 50,31,226; 60,13,159$

Write down the greatest and smallest number of $3$ digits that can be formed using the digits $6, 9, 0$ using each digit only once.

Write the greatest and smallest $7$-digit number using five different digits.

Write the successor of the following:

$29,099$

Write the successor of the following:

$3,78,915$