A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1622880 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 16 18 20 21 23 24 28 30 32 35 36 40 42 45 46 48 49 56 60 63 69 70 72 80 84 90 92 96 98 105 112 115 120 126 138 140 144 147 160 161 168 180 184 196 207 210 224 230 240 245 252 276 280 288 294 315 322 336 345 360 368 392 414 420 441 460 480 483 490 504 552 560 588 630 644 672 690 720 735 736 784 805 828 840 882 920 966 980 1,008 1,035 1,104 1,120 1,127 1,176 1,260 1,288 1,380 1,440 1,449 1,470 1,568 1,610 1,656 1,680 1,764 1,840 1,932 1,960 2,016 2,070 2,205 2,208 2,254 2,352 2,415 2,520 2,576 2,760 2,898 2,940 3,220 3,312 3,360 3,381 3,528 3,680 3,864 3,920 4,140 4,410 4,508 4,704 4,830 5,040 5,152 5,520 5,635 5,796 5,880 6,440 6,624 6,762 7,056 7,245 7,728 7,840 8,280 8,820 9,016 9,660 10,080 10,143 11,040 11,270 11,592 11,760 12,880 13,524 14,112 14,490 15,456 16,560 16,905 17,640 18,032 19,320 20,286 22,540 23,184 23,520 25,760 27,048 28,980 33,120 33,810 35,280 36,064 38,640 40,572 45,080 46,368 50,715 54,096 57,960 67,620 70,560 77,280 81,144 90,160 101,430 108,192 115,920 135,240 162,288 180,320 202,860 231,840 270,480 324,576 405,720 540,960 811,440 and 1,622,880, with no remainder.
Since 1,622,880 cannot be divided by just 1 and 1,622,880, it is not a prime number.