A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2136240 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 23 24 27 30 36 40 43 45 46 48 54 60 69 72 80 86 90 92 108 115 120 129 135 138 144 172 180 184 207 215 216 230 240 258 270 276 344 345 360 368 387 414 430 432 460 516 540 552 621 645 688 690 720 774 828 860 920 989 1,032 1,035 1,080 1,104 1,161 1,242 1,290 1,380 1,548 1,656 1,720 1,840 1,935 1,978 2,064 2,070 2,160 2,322 2,484 2,580 2,760 2,967 3,096 3,105 3,312 3,440 3,870 3,956 4,140 4,644 4,945 4,968 5,160 5,520 5,805 5,934 6,192 6,210 7,740 7,912 8,280 8,901 9,288 9,890 9,936 10,320 11,610 11,868 12,420 14,835 15,480 15,824 16,560 17,802 18,576 19,780 23,220 23,736 24,840 26,703 29,670 30,960 35,604 39,560 44,505 46,440 47,472 49,680 53,406 59,340 71,208 79,120 89,010 92,880 106,812 118,680 133,515 142,416 178,020 213,624 237,360 267,030 356,040 427,248 534,060 712,080 1,068,120 and 2,136,240, with no remainder.
Since 2,136,240 cannot be divided by just 1 and 2,136,240, it is not a prime number.