A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2841720 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 14 15 17 20 21 24 28 30 34 35 40 42 51 56 60 68 70 84 85 102 105 119 120 136 140 168 170 199 204 210 238 255 280 340 357 398 408 420 476 510 595 597 680 714 796 840 952 995 1,020 1,190 1,194 1,393 1,428 1,592 1,785 1,990 2,040 2,380 2,388 2,786 2,856 2,985 3,383 3,570 3,980 4,179 4,760 4,776 5,572 5,970 6,766 6,965 7,140 7,960 8,358 10,149 11,144 11,940 13,532 13,930 14,280 16,716 16,915 20,298 20,895 23,681 23,880 27,064 27,860 33,432 33,830 40,596 41,790 47,362 50,745 55,720 67,660 71,043 81,192 83,580 94,724 101,490 118,405 135,320 142,086 167,160 189,448 202,980 236,810 284,172 355,215 405,960 473,620 568,344 710,430 947,240 1,420,860 and 2,841,720, with no remainder.
Since 2,841,720 cannot be divided by just 1 and 2,841,720, it is not a prime number.