A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3289248 can be evenly divided by 1 2 3 4 6 8 9 12 16 18 24 27 32 36 47 48 54 72 81 94 96 108 141 144 162 188 216 243 282 288 324 376 423 432 486 564 648 729 752 846 864 972 1,128 1,269 1,296 1,458 1,504 1,692 1,944 2,187 2,256 2,538 2,592 2,916 3,384 3,807 3,888 4,374 4,512 5,076 5,832 6,768 7,614 7,776 8,748 10,152 11,421 11,664 13,536 15,228 17,496 20,304 22,842 23,328 30,456 34,263 34,992 40,608 45,684 60,912 68,526 69,984 91,368 102,789 121,824 137,052 182,736 205,578 274,104 365,472 411,156 548,208 822,312 1,096,416 1,644,624 and 3,289,248, with no remainder.
Since 3,289,248 cannot be divided by just 1 and 3,289,248, it is not a prime number.