A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2121504 can be evenly divided by 1 2 3 4 6 7 8 11 12 14 16 21 22 24 28 32 33 41 42 44 48 49 56 66 77 82 84 88 96 98 112 123 132 147 154 164 168 176 196 224 231 246 264 287 294 308 328 336 352 392 451 462 492 528 539 574 588 616 656 672 784 861 902 924 984 1,056 1,078 1,148 1,176 1,232 1,312 1,353 1,568 1,617 1,722 1,804 1,848 1,968 2,009 2,156 2,296 2,352 2,464 2,706 3,157 3,234 3,444 3,608 3,696 3,936 4,018 4,312 4,592 4,704 5,412 6,027 6,314 6,468 6,888 7,216 7,392 8,036 8,624 9,184 9,471 10,824 12,054 12,628 12,936 13,776 14,432 16,072 17,248 18,942 21,648 22,099 24,108 25,256 25,872 27,552 32,144 37,884 43,296 44,198 48,216 50,512 51,744 64,288 66,297 75,768 88,396 96,432 101,024 132,594 151,536 176,792 192,864 265,188 303,072 353,584 530,376 707,168 1,060,752 and 2,121,504, with no remainder.
Since 2,121,504 cannot be divided by just 1 and 2,121,504, it is not a prime number.