A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 739440 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 13 15 16 18 20 24 26 30 36 39 40 45 48 52 60 65 72 78 79 80 90 104 117 120 130 144 156 158 180 195 208 234 237 240 260 312 316 360 390 395 468 474 520 585 624 632 711 720 780 790 936 948 1,027 1,040 1,170 1,185 1,264 1,422 1,560 1,580 1,872 1,896 2,054 2,340 2,370 2,844 3,081 3,120 3,160 3,555 3,792 4,108 4,680 4,740 5,135 5,688 6,162 6,320 7,110 8,216 9,243 9,360 9,480 10,270 11,376 12,324 14,220 15,405 16,432 18,486 18,960 20,540 24,648 28,440 30,810 36,972 41,080 46,215 49,296 56,880 61,620 73,944 82,160 92,430 123,240 147,888 184,860 246,480 369,720 and 739,440, with no remainder.
Since 739,440 cannot be divided by just 1 and 739,440, it is not a prime number.