A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 978180 can be evenly divided by 1 2 3 4 5 6 7 10 12 14 15 17 20 21 28 30 34 35 42 51 60 68 70 84 85 102 105 119 137 140 170 204 210 238 255 274 340 357 411 420 476 510 548 595 685 714 822 959 1,020 1,190 1,370 1,428 1,644 1,785 1,918 2,055 2,329 2,380 2,740 2,877 3,570 3,836 4,110 4,658 4,795 5,754 6,987 7,140 8,220 9,316 9,590 11,508 11,645 13,974 14,385 16,303 19,180 23,290 27,948 28,770 32,606 34,935 46,580 48,909 57,540 65,212 69,870 81,515 97,818 139,740 163,030 195,636 244,545 326,060 489,090 and 978,180, with no remainder.
Since 978,180 cannot be divided by just 1 and 978,180, it is not a prime number.