Task: How many different ways can £2 be made using any number of coins?

Find the sum of all products whose multiplicand/multiplier/product identity can be written as a 1 through 9 pandigital.

Find the denominator of the four non-trivial examples.

Find the sum of all numbers which are equal to the sum of the factorial of their digits.

How many circular primes are there below one million?

Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2.

Find the sum of the only eleven primes that are both truncatable from left to right and right to left.

What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, … , n) where n > 1?

For which value of p ≤ 1000, is the number of solutions maximised?

Find the value of the expression d1 × d10 × d100 × d1000 × d10000 × d100000 × d1000000.