A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2124320 can be evenly divided by 1 2 4 5 8 10 11 16 17 20 22 32 34 40 44 55 68 71 80 85 88 110 136 142 160 170 176 187 220 272 284 340 352 355 374 440 544 568 680 710 748 781 880 935 1,136 1,207 1,360 1,420 1,496 1,562 1,760 1,870 2,272 2,414 2,720 2,840 2,992 3,124 3,740 3,905 4,828 5,680 5,984 6,035 6,248 7,480 7,810 9,656 11,360 12,070 12,496 13,277 14,960 15,620 19,312 24,140 24,992 26,554 29,920 31,240 38,624 48,280 53,108 62,480 66,385 96,560 106,216 124,960 132,770 193,120 212,432 265,540 424,864 531,080 1,062,160 and 2,124,320, with no remainder.
Since 2,124,320 cannot be divided by just 1 and 2,124,320, it is not a prime number.