A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7421568 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 56 64 66 77 84 88 96 112 128 132 154 168 176 192 224 231 251 264 308 336 352 384 448 462 502 528 616 672 704 753 896 924 1,004 1,056 1,232 1,344 1,408 1,506 1,757 1,848 2,008 2,112 2,464 2,688 2,761 3,012 3,514 3,696 4,016 4,224 4,928 5,271 5,522 6,024 7,028 7,392 8,032 8,283 9,856 10,542 11,044 12,048 14,056 14,784 16,064 16,566 19,327 21,084 22,088 24,096 28,112 29,568 32,128 33,132 38,654 42,168 44,176 48,192 56,224 57,981 66,264 77,308 84,336 88,352 96,384 112,448 115,962 132,528 154,616 168,672 176,704 224,896 231,924 265,056 309,232 337,344 353,408 463,848 530,112 618,464 674,688 927,696 1,060,224 1,236,928 1,855,392 2,473,856 3,710,784 and 7,421,568, with no remainder.
Since 7,421,568 cannot be divided by just 1 and 7,421,568, it is not a prime number.