When 100²⁵−25 is written in decimal notation, sum of digits is

What is the last digit of the sum S = 9²⁷ + 27⁹ ?

What is the digit at the 100th place of number (225)⁴⁰ ?

The value of a 2-digit number is 5 times the sum of the digits. What is the product of the digits ?

The sum of digits of a 2-digit number is 12. When the digits are reversed, the number becomes greater by eighteen. What is the difference between the digits in the number ?

What is the sum of all the divisors of 256?