A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7828260 can be evenly divided by 1 2 3 4 5 6 10 11 12 15 20 22 29 30 33 44 55 58 60 66 87 110 116 132 145 165 174 220 290 319 330 348 409 435 580 638 660 818 870 957 1,227 1,276 1,595 1,636 1,740 1,914 2,045 2,454 3,190 3,828 4,090 4,499 4,785 4,908 6,135 6,380 8,180 8,998 9,570 11,861 12,270 13,497 17,996 19,140 22,495 23,722 24,540 26,994 35,583 44,990 47,444 53,988 59,305 67,485 71,166 89,980 118,610 130,471 134,970 142,332 177,915 237,220 260,942 269,940 355,830 391,413 521,884 652,355 711,660 782,826 1,304,710 1,565,652 1,957,065 2,609,420 3,914,130 and 7,828,260, with no remainder.
Since 7,828,260 cannot be divided by just 1 and 7,828,260, it is not a prime number.