A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7555548 can be evenly divided by 1 2 3 4 6 7 11 12 13 14 17 21 22 26 28 33 34 37 39 42 44 51 52 66 68 74 77 78 84 91 102 111 119 132 143 148 154 156 182 187 204 221 222 231 238 259 273 286 308 357 364 374 407 429 442 444 462 476 481 518 546 561 572 629 663 714 748 777 814 858 884 924 962 1,001 1,036 1,092 1,122 1,221 1,258 1,309 1,326 1,428 1,443 1,547 1,554 1,628 1,716 1,887 1,924 2,002 2,244 2,431 2,442 2,516 2,618 2,652 2,849 2,886 3,003 3,094 3,108 3,367 3,774 3,927 4,004 4,403 4,641 4,862 4,884 5,236 5,291 5,698 5,772 6,006 6,188 6,734 6,919 7,293 7,548 7,854 8,177 8,547 8,806 9,282 9,724 10,101 10,582 11,396 12,012 13,209 13,468 13,838 14,586 15,708 15,873 16,354 17,017 17,094 17,612 18,564 20,202 20,757 21,164 24,531 26,418 27,676 29,172 31,746 32,708 34,034 34,188 37,037 40,404 41,514 48,433 49,062 51,051 52,836 57,239 63,492 68,068 74,074 83,028 89,947 96,866 98,124 102,102 111,111 114,478 145,299 148,148 171,717 179,894 193,732 204,204 222,222 228,956 269,841 290,598 343,434 359,788 444,444 539,682 581,196 629,629 686,868 1,079,364 1,259,258 1,888,887 2,518,516 3,777,774 and 7,555,548, with no remainder.
Since 7,555,548 cannot be divided by just 1 and 7,555,548, it is not a prime number.