A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3117576 can be evenly divided by 1 2 3 4 6 7 8 11 12 14 21 22 24 28 33 42 44 49 56 66 77 84 88 98 132 147 154 168 196 231 241 264 294 308 392 462 482 539 588 616 723 924 964 1,078 1,176 1,446 1,617 1,687 1,848 1,928 2,156 2,651 2,892 3,234 3,374 4,312 5,061 5,302 5,784 6,468 6,748 7,953 10,122 10,604 11,809 12,936 13,496 15,906 18,557 20,244 21,208 23,618 31,812 35,427 37,114 40,488 47,236 55,671 63,624 70,854 74,228 94,472 111,342 129,899 141,708 148,456 222,684 259,798 283,416 389,697 445,368 519,596 779,394 1,039,192 1,558,788 and 3,117,576, with no remainder.
Since 3,117,576 cannot be divided by just 1 and 3,117,576, it is not a prime number.