A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3147768 can be evenly divided by 1 2 3 4 6 8 9 12 13 18 19 24 26 27 36 38 39 52 54 57 59 72 76 78 104 108 114 117 118 152 156 171 177 216 228 234 236 247 312 342 351 354 456 468 472 494 513 531 684 702 708 741 767 936 988 1,026 1,062 1,121 1,368 1,404 1,416 1,482 1,534 1,593 1,976 2,052 2,124 2,223 2,242 2,301 2,808 2,964 3,068 3,186 3,363 4,104 4,248 4,446 4,484 4,602 5,928 6,136 6,372 6,669 6,726 6,903 8,892 8,968 9,204 10,089 12,744 13,338 13,452 13,806 14,573 17,784 18,408 20,178 20,709 26,676 26,904 27,612 29,146 30,267 40,356 41,418 43,719 53,352 55,224 58,292 60,534 80,712 82,836 87,438 116,584 121,068 131,157 165,672 174,876 242,136 262,314 349,752 393,471 524,628 786,942 1,049,256 1,573,884 and 3,147,768, with no remainder.
Since 3,147,768 cannot be divided by just 1 and 3,147,768, it is not a prime number.