A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1731450 can be evenly divided by 1 2 3 5 6 7 10 14 15 17 21 25 30 34 35 42 50 51 70 75 85 97 102 105 119 150 170 175 194 210 238 255 291 350 357 425 485 510 525 582 595 679 714 850 970 1,050 1,190 1,275 1,358 1,455 1,649 1,785 2,037 2,425 2,550 2,910 2,975 3,298 3,395 3,570 4,074 4,850 4,947 5,950 6,790 7,275 8,245 8,925 9,894 10,185 11,543 14,550 16,490 16,975 17,850 20,370 23,086 24,735 33,950 34,629 41,225 49,470 50,925 57,715 69,258 82,450 101,850 115,430 123,675 173,145 247,350 288,575 346,290 577,150 865,725 and 1,731,450, with no remainder.
Since 1,731,450 cannot be divided by just 1 and 1,731,450, it is not a prime number.