How many positive integers b have the property that `log_(b)729` is a positive integer ?

How many two-digit positive integers N have the property that the sum of N and the number obtained reversing the order of the digits of N is a perfect square?

How many positive integers less than 1000 have the property that the sum of the digits of each such number is divisible by 7 and the number itself is divisible by 3?

How many positive integers less than 1000 have the property that the sum of the digits of each such number is divisible by 7 and the number itself is divisible by 3 ?

If a and b are positive integers then

How many positive integers have characteristics 2 when base is 5.

How many positive integers have characteristics 2 when base is 5.

Write a positive integer and a negative integer whose sum is a positive integer.

Write the expansion of (a-b)^n, n is a positive integer