A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2126280 can be evenly divided by 1 2 3 4 5 6 8 10 12 13 15 20 24 26 29 30 39 40 47 52 58 60 65 78 87 94 104 116 120 130 141 145 156 174 188 195 232 235 260 282 290 312 348 376 377 390 435 470 520 564 580 611 696 705 754 780 870 940 1,128 1,131 1,160 1,222 1,363 1,410 1,508 1,560 1,740 1,833 1,880 1,885 2,262 2,444 2,726 2,820 3,016 3,055 3,480 3,666 3,770 4,089 4,524 4,888 5,452 5,640 5,655 6,110 6,815 7,332 7,540 8,178 9,048 9,165 10,904 11,310 12,220 13,630 14,664 15,080 16,356 17,719 18,330 20,445 22,620 24,440 27,260 32,712 35,438 36,660 40,890 45,240 53,157 54,520 70,876 73,320 81,780 88,595 106,314 141,752 163,560 177,190 212,628 265,785 354,380 425,256 531,570 708,760 1,063,140 and 2,126,280, with no remainder.
Since 2,126,280 cannot be divided by just 1 and 2,126,280, it is not a prime number.