A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6454240 can be evenly divided by 1 2 4 5 8 10 13 16 20 26 29 32 40 52 58 65 80 104 107 116 130 145 160 208 214 232 260 290 377 416 428 464 520 535 580 754 856 928 1,040 1,070 1,160 1,391 1,508 1,712 1,885 2,080 2,140 2,320 2,782 3,016 3,103 3,424 3,770 4,280 4,640 5,564 6,032 6,206 6,955 7,540 8,560 11,128 12,064 12,412 13,910 15,080 15,515 17,120 22,256 24,824 27,820 30,160 31,030 40,339 44,512 49,648 55,640 60,320 62,060 80,678 99,296 111,280 124,120 161,356 201,695 222,560 248,240 322,712 403,390 496,480 645,424 806,780 1,290,848 1,613,560 3,227,120 and 6,454,240, with no remainder.
Since 6,454,240 cannot be divided by just 1 and 6,454,240, it is not a prime number.