A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7479738 can be evenly divided by 1 2 3 6 7 9 14 18 21 23 29 42 46 58 63 69 87 89 126 138 161 174 178 203 207 261 267 322 406 414 483 522 534 609 623 667 801 966 1,218 1,246 1,334 1,449 1,602 1,827 1,869 2,001 2,047 2,581 2,898 3,654 3,738 4,002 4,094 4,669 5,162 5,607 6,003 6,141 7,743 9,338 11,214 12,006 12,282 14,007 14,329 15,486 18,067 18,423 23,229 28,014 28,658 36,134 36,846 42,021 42,987 46,458 54,201 59,363 84,042 85,974 108,402 118,726 128,961 162,603 178,089 257,922 325,206 356,178 415,541 534,267 831,082 1,068,534 1,246,623 2,493,246 3,739,869 and 7,479,738, with no remainder.
Since 7,479,738 cannot be divided by just 1 and 7,479,738, it is not a prime number.