A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 992880 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 16 18 20 21 24 28 30 35 36 40 42 45 48 56 60 63 70 72 80 84 90 105 112 120 126 140 144 168 180 197 210 240 252 280 315 336 360 394 420 504 560 591 630 720 788 840 985 1,008 1,182 1,260 1,379 1,576 1,680 1,773 1,970 2,364 2,520 2,758 2,955 3,152 3,546 3,940 4,137 4,728 5,040 5,516 5,910 6,895 7,092 7,880 8,274 8,865 9,456 11,032 11,820 12,411 13,790 14,184 15,760 16,548 17,730 20,685 22,064 23,640 24,822 27,580 28,368 33,096 35,460 41,370 47,280 49,644 55,160 62,055 66,192 70,920 82,740 99,288 110,320 124,110 141,840 165,480 198,576 248,220 330,960 496,440 and 992,880, with no remainder.
Since 992,880 cannot be divided by just 1 and 992,880, it is not a prime number.