A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3212748 can be evenly divided by 1 2 3 4 6 7 9 11 12 14 18 19 21 22 28 33 36 38 42 44 57 61 63 66 76 77 84 99 114 122 126 132 133 154 171 183 198 209 228 231 244 252 266 308 342 366 396 399 418 427 462 532 549 627 671 684 693 732 798 836 854 924 1,098 1,159 1,197 1,254 1,281 1,342 1,386 1,463 1,596 1,708 1,881 2,013 2,196 2,318 2,394 2,508 2,562 2,684 2,772 2,926 3,477 3,762 3,843 4,026 4,389 4,636 4,697 4,788 5,124 5,852 6,039 6,954 7,524 7,686 8,052 8,113 8,778 9,394 10,431 12,078 12,749 13,167 13,908 14,091 15,372 16,226 17,556 18,788 20,862 24,156 24,339 25,498 26,334 28,182 32,452 38,247 41,724 42,273 48,678 50,996 52,668 56,364 73,017 76,494 84,546 89,243 97,356 114,741 146,034 152,988 169,092 178,486 229,482 267,729 292,068 356,972 458,964 535,458 803,187 1,070,916 1,606,374 and 3,212,748, with no remainder.
Since 3,212,748 cannot be divided by just 1 and 3,212,748, it is not a prime number.