Let S be the set of all positive integers having at most 4 digits and such that each of the digits is 0 or 1. What is the greatest prime factor of the sum of all the numbers in S?

If n=p²and p is a prime number greater than 5, what is the units digit of n²?

An "Armstrong number" is an n-digit number that is equal to the sum of the nth powers of its individual digits. For example, 153 is an Armstrong number because it has 3 digits and 1³+5³+3³=153. What is the digit k in the Armstrong number 1,6k4？

Five integers between 10 and 99, inclusive, are to be formed by using each of the ten digits exactly once in such a way that the sum of the five integers is as small as possible.What is the greatest possible integer that could be among these five numbers?

If the product of the integers w,x, y, and z is 770, and if1 < w < x < y < z, what is the value of w + z?

If x < y < z and y - x > 5, where x is an even integer and y and z are odd integers, what is the least possible value of z-x?

If Whitmey wrote the decimal representations for the first 300 positive integer multiples of 5 and did not write any other numbers, how many times would she have written the digit 5?

Of the following, which is greatest?

 How many positive integers n have the property that both 3n andn/3 are 4-digit integers?

The difference 942-249 is a positive multiple of 7. If a, b, and c are nonzero digits, how many 3-digit numbers abc are possible such that the difference abc - cba is a positive multiple of 7?