A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6542280 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 17 18 20 24 30 34 36 40 45 51 60 68 72 85 90 102 120 136 153 170 180 204 255 306 340 360 408 510 612 680 765 1,020 1,069 1,224 1,530 2,040 2,138 3,060 3,207 4,276 5,345 6,120 6,414 8,552 9,621 10,690 12,828 16,035 18,173 19,242 21,380 25,656 32,070 36,346 38,484 42,760 48,105 54,519 64,140 72,692 76,968 90,865 96,210 109,038 128,280 145,384 163,557 181,730 192,420 218,076 272,595 327,114 363,460 384,840 436,152 545,190 654,228 726,920 817,785 1,090,380 1,308,456 1,635,570 2,180,760 3,271,140 and 6,542,280, with no remainder.
Since 6,542,280 cannot be divided by just 1 and 6,542,280, it is not a prime number.