A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1873080 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 43 44 45 55 60 66 72 86 88 90 99 110 120 121 129 132 165 172 180 198 215 220 242 258 264 330 344 360 363 387 396 430 440 473 484 495 516 605 645 660 726 774 792 860 946 968 990 1,032 1,089 1,210 1,290 1,320 1,419 1,452 1,548 1,720 1,815 1,892 1,935 1,980 2,178 2,365 2,420 2,580 2,838 2,904 3,096 3,630 3,784 3,870 3,960 4,257 4,356 4,730 4,840 5,160 5,203 5,445 5,676 7,095 7,260 7,740 8,514 8,712 9,460 10,406 10,890 11,352 14,190 14,520 15,480 15,609 17,028 18,920 20,812 21,285 21,780 26,015 28,380 31,218 34,056 41,624 42,570 43,560 46,827 52,030 56,760 62,436 78,045 85,140 93,654 104,060 124,872 156,090 170,280 187,308 208,120 234,135 312,180 374,616 468,270 624,360 936,540 and 1,873,080, with no remainder.
Since 1,873,080 cannot be divided by just 1 and 1,873,080, it is not a prime number.