A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2316720 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 14 15 16 20 21 24 28 30 35 40 42 48 49 56 60 70 80 84 98 105 112 120 140 147 168 196 197 210 240 245 280 294 336 392 394 420 490 560 588 591 735 784 788 840 980 985 1,176 1,182 1,379 1,470 1,576 1,680 1,960 1,970 2,352 2,364 2,758 2,940 2,955 3,152 3,920 3,940 4,137 4,728 5,516 5,880 5,910 6,895 7,880 8,274 9,456 9,653 11,032 11,760 11,820 13,790 15,760 16,548 19,306 20,685 22,064 23,640 27,580 28,959 33,096 38,612 41,370 47,280 48,265 55,160 57,918 66,192 77,224 82,740 96,530 110,320 115,836 144,795 154,448 165,480 193,060 231,672 289,590 330,960 386,120 463,344 579,180 772,240 1,158,360 and 2,316,720, with no remainder.
Since 2,316,720 cannot be divided by just 1 and 2,316,720, it is not a prime number.