Four different prime numbers 5, 7, 17 and 19 such that the sum of any three of them is also a prime. Are there 5 different positive primes such that the sum of any three of them is also a prime?
Prime number 31 can be expressed in the form n^5 -1, where n=2. Are there any other primes that can be expressed this way?
There are 168 primes less than 1,000. What is the sum of the prime numbers less than 1,000?
(a) 11,555 (b) 76,127 (c) 57,298 (d) 81,722
First 17 positive integers (1..17) are rearranged into a sequence such that the sum of any two adjacent terms is a perfect square. What is the sum of the first and last terms of this sequence?
Is it possible to write down 1,2,3..100 in some order (one after an other), such that the sum of any two adjacent numbers is a prime number?
