A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2205216 can be evenly divided by 1 2 3 4 6 8 9 12 13 16 18 19 24 26 31 32 36 38 39 48 52 57 62 72 76 78 93 96 104 114 117 124 144 152 156 171 186 208 228 234 247 248 279 288 304 312 342 372 403 416 456 468 494 496 558 589 608 624 684 741 744 806 912 936 988 992 1,116 1,178 1,209 1,248 1,368 1,482 1,488 1,612 1,767 1,824 1,872 1,976 2,223 2,232 2,356 2,418 2,736 2,964 2,976 3,224 3,534 3,627 3,744 3,952 4,446 4,464 4,712 4,836 5,301 5,472 5,928 6,448 7,068 7,254 7,657 7,904 8,892 8,928 9,424 9,672 10,602 11,856 12,896 14,136 14,508 15,314 17,784 18,848 19,344 21,204 22,971 23,712 28,272 29,016 30,628 35,568 38,688 42,408 45,942 56,544 58,032 61,256 68,913 71,136 84,816 91,884 116,064 122,512 137,826 169,632 183,768 245,024 275,652 367,536 551,304 735,072 1,102,608 and 2,205,216, with no remainder.
Since 2,205,216 cannot be divided by just 1 and 2,205,216, it is not a prime number.