A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1160280 can be evenly divided by 1 2 3 4 5 6 8 9 10 11 12 15 18 20 22 24 30 33 36 40 44 45 55 60 66 72 88 90 99 110 120 132 165 180 198 220 264 293 330 360 396 440 495 586 660 792 879 990 1,172 1,320 1,465 1,758 1,980 2,344 2,637 2,930 3,223 3,516 3,960 4,395 5,274 5,860 6,446 7,032 8,790 9,669 10,548 11,720 12,892 13,185 16,115 17,580 19,338 21,096 25,784 26,370 29,007 32,230 35,160 38,676 48,345 52,740 58,014 64,460 77,352 96,690 105,480 116,028 128,920 145,035 193,380 232,056 290,070 386,760 580,140 and 1,160,280, with no remainder.
Since 1,160,280 cannot be divided by just 1 and 1,160,280, it is not a prime number.