If N=3¹⁰+3¹¹+3¹²+3¹³, how many positive factors does N have?

Seven times a two-digit positive number is equal to four times the number obtained by reversing the order of the digits. How many such two-digit numbers are there?

How many times the digit 9 occurs in the numbers from 100 to 999?

What is the median of all possible factors of 120 ?

How many three-digit numbers are divisible by 5?

Consider the following numbers : 1. 437 2. 797 3. 1073 How many of the above numbers are prime ?