Erdős–Mollin–Walsh conjecture

A powerful number is a positive integer m such that for every prime number p dividing m, p2 also divides m. Equivalently, a powerful number is the product of a square and a cube, that is, a number m of the form m = a2b3, where a and b are positive integers. Paul Erdős and George Szekeres studied such numbers and Solomon W. Golomb named such numbers powerful. Powerful numbers are also known as squarefull, square-full, or 2-full.