A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2559150 can be evenly divided by 1 2 3 5 6 9 10 11 15 18 22 25 30 33 45 47 50 55 66 75 90 94 99 110 121 141 150 165 198 225 235 242 275 282 330 363 423 450 470 495 517 550 605 705 726 825 846 990 1,034 1,089 1,175 1,210 1,410 1,551 1,650 1,815 2,115 2,178 2,350 2,475 2,585 3,025 3,102 3,525 3,630 4,230 4,653 4,950 5,170 5,445 5,687 6,050 7,050 7,755 9,075 9,306 10,575 10,890 11,374 12,925 15,510 17,061 18,150 21,150 23,265 25,850 27,225 28,435 34,122 38,775 46,530 51,183 54,450 56,870 77,550 85,305 102,366 116,325 142,175 170,610 232,650 255,915 284,350 426,525 511,830 853,050 1,279,575 and 2,559,150, with no remainder.
Since 2,559,150 cannot be divided by just 1 and 2,559,150, it is not a prime number.