What is the largest n-digit pandigital prime that exists?
How many triangle words does the list of common English words contain?
Find the sum of all pandigital numbers with an unusual sub-string divisibility property.
Find the smallest pair of pentagonal numbers whose sum and difference is pentagonal.
After 40755, what is the next triangle number that is also pentagonal and hexagonal?
What is the smallest odd composite that cannot be written as the sum of a prime and twice a square?
Find the first four consecutive integers to have four distinct primes factors.
Find the last ten digits of 11 + 22 + … + 10001000.
Find arithmetic sequences, made of prime terms, whose four digits are permutations of each other.