A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1270920 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 14 15 17 20 21 24 28 30 34 35 40 42 51 56 60 68 70 84 85 89 102 105 119 120 136 140 168 170 178 204 210 238 255 267 280 340 356 357 408 420 445 476 510 534 595 623 680 712 714 840 890 952 1,020 1,068 1,190 1,246 1,335 1,428 1,513 1,780 1,785 1,869 2,040 2,136 2,380 2,492 2,670 2,856 3,026 3,115 3,560 3,570 3,738 4,539 4,760 4,984 5,340 6,052 6,230 7,140 7,476 7,565 9,078 9,345 10,591 10,680 12,104 12,460 14,280 14,952 15,130 18,156 18,690 21,182 22,695 24,920 30,260 31,773 36,312 37,380 42,364 45,390 52,955 60,520 63,546 74,760 84,728 90,780 105,910 127,092 158,865 181,560 211,820 254,184 317,730 423,640 635,460 and 1,270,920, with no remainder.
Since 1,270,920 cannot be divided by just 1 and 1,270,920, it is not a prime number.