How many numbers with distinct digits are possible product of whose digits is 28?
A page is torn from a novel. The sum of the remaining digits is 10000. What is the sum of the two page-numbers on the torn page of this novel?
A 4-digit number of the form aabb is a perfect square. What is the value of a - b?
What are the last two digits of the number 745?
n2 + 5n + 6 is a multiple of 6. n is natural number less than 100. How many values can n take?
[x] is the greatest integer less than or equal to x. Find the number of positive integers n such that .
Positive numbers 1 to 55, inclusive are placed in 5 groups of 11 numbers each. What is the maximum possible average of the medians of the 5 groups?
N is an 80-digit positive integer (in the decimal scale). All digits except the 44th digit (from the left) are 2. If N is divisible by 13, find the 26th digit?