A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7451640 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 18 20 21 24 28 30 35 36 40 42 45 56 60 63 70 72 84 90 105 120 126 140 168 180 210 252 280 315 360 420 504 630 840 1,260 2,520 2,957 5,914 8,871 11,828 14,785 17,742 20,699 23,656 26,613 29,570 35,484 41,398 44,355 53,226 59,140 62,097 70,968 82,796 88,710 103,495 106,452 118,280 124,194 133,065 165,592 177,420 186,291 206,990 212,904 248,388 266,130 310,485 354,840 372,582 413,980 496,776 532,260 620,970 745,164 827,960 931,455 1,064,520 1,241,940 1,490,328 1,862,910 2,483,880 3,725,820 and 7,451,640, with no remainder.
Since 7,451,640 cannot be divided by just 1 and 7,451,640, it is not a prime number.