A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3777312 can be evenly divided by 1 2 3 4 6 7 8 11 12 14 16 21 22 24 28 32 33 42 44 48 49 56 66 73 77 84 88 96 98 112 132 146 147 154 168 176 196 219 224 231 264 292 294 308 336 352 392 438 462 511 528 539 584 588 616 672 784 803 876 924 1,022 1,056 1,078 1,168 1,176 1,232 1,533 1,568 1,606 1,617 1,752 1,848 2,044 2,156 2,336 2,352 2,409 2,464 3,066 3,212 3,234 3,504 3,577 3,696 4,088 4,312 4,704 4,818 5,621 6,132 6,424 6,468 7,008 7,154 7,392 8,176 8,624 9,636 10,731 11,242 12,264 12,848 12,936 14,308 16,352 16,863 17,248 19,272 21,462 22,484 24,528 25,696 25,872 28,616 33,726 38,544 39,347 42,924 44,968 49,056 51,744 57,232 67,452 77,088 78,694 85,848 89,936 114,464 118,041 134,904 157,388 171,696 179,872 236,082 269,808 314,776 343,392 472,164 539,616 629,552 944,328 1,259,104 1,888,656 and 3,777,312, with no remainder.
Since 3,777,312 cannot be divided by just 1 and 3,777,312, it is not a prime number.