A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 242550 can be evenly divided by 1 2 3 5 6 7 9 10 11 14 15 18 21 22 25 30 33 35 42 45 49 50 55 63 66 70 75 77 90 98 99 105 110 126 147 150 154 165 175 198 210 225 231 245 275 294 315 330 350 385 441 450 462 490 495 525 539 550 630 693 735 770 825 882 990 1,050 1,078 1,155 1,225 1,386 1,470 1,575 1,617 1,650 1,925 2,205 2,310 2,450 2,475 2,695 3,150 3,234 3,465 3,675 3,850 4,410 4,851 4,950 5,390 5,775 6,930 7,350 8,085 9,702 11,025 11,550 13,475 16,170 17,325 22,050 24,255 26,950 34,650 40,425 48,510 80,850 121,275 and 242,550, with no remainder.
Since 242,550 cannot be divided by just 1 and 242,550, it is not a prime number.