Problem

Source: 2019 Saudi Arabia March Camp Test 3.3

Tags: Coloring, combinatorics



All of the numbers 1,2,3,...,1000000 are initially colored black. On each move it is possible to choose the number x (among the colored numbers) and change the color of x and of all of the numbers that are not co-prime with x (black into white, white into black). Is it possible to color all of the numbers white?