Landau's problems

Etymology
Listed by at the International Congress of Mathematicians in 1912.

Proper noun

 * 1)  Four basic unsolved problems about prime numbers: (i) is Goldbach's conjecture true?; (ii) is the twin prime conjecture true?; (iii) is Legendre's conjecture true?; (iv) are there infinitely many primes p such that p&thinsp;−&thinsp;1 is a perfect square?