A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7427376 can be evenly divided by 1 2 3 4 6 8 9 11 12 16 18 22 24 27 33 36 44 48 54 66 72 81 88 99 108 132 144 162 176 198 216 264 297 324 396 432 521 528 594 648 792 891 1,042 1,188 1,296 1,563 1,584 1,782 2,084 2,376 3,126 3,564 4,168 4,689 4,752 5,731 6,252 7,128 8,336 9,378 11,462 12,504 14,067 14,256 17,193 18,756 22,924 25,008 28,134 34,386 37,512 42,201 45,848 51,579 56,268 68,772 75,024 84,402 91,696 103,158 112,536 137,544 154,737 168,804 206,316 225,072 275,088 309,474 337,608 412,632 464,211 618,948 675,216 825,264 928,422 1,237,896 1,856,844 2,475,792 3,713,688 and 7,427,376, with no remainder.
Since 7,427,376 cannot be divided by just 1 and 7,427,376, it is not a prime number.