A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6308940 can be evenly divided by 1 2 3 4 5 6 10 11 12 15 20 22 30 33 44 55 60 66 79 110 121 132 158 165 220 237 242 316 330 363 395 474 484 605 660 726 790 869 948 1,185 1,210 1,331 1,452 1,580 1,738 1,815 2,370 2,420 2,607 2,662 3,476 3,630 3,993 4,345 4,740 5,214 5,324 6,655 7,260 7,986 8,690 9,559 10,428 13,035 13,310 15,972 17,380 19,118 19,965 26,070 26,620 28,677 38,236 39,930 47,795 52,140 57,354 79,860 95,590 105,149 114,708 143,385 191,180 210,298 286,770 315,447 420,596 525,745 573,540 630,894 1,051,490 1,261,788 1,577,235 2,102,980 3,154,470 and 6,308,940, with no remainder.
Since 6,308,940 cannot be divided by just 1 and 6,308,940, it is not a prime number.