A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 739860 can be evenly divided by 1 2 3 4 5 6 10 11 12 15 19 20 22 30 33 38 44 55 57 59 60 66 76 95 110 114 118 132 165 177 190 209 220 228 236 285 295 330 354 380 418 570 590 627 649 660 708 836 885 1,045 1,121 1,140 1,180 1,254 1,298 1,770 1,947 2,090 2,242 2,508 2,596 3,135 3,245 3,363 3,540 3,894 4,180 4,484 5,605 6,270 6,490 6,726 7,788 9,735 11,210 12,331 12,540 12,980 13,452 16,815 19,470 22,420 24,662 33,630 36,993 38,940 49,324 61,655 67,260 73,986 123,310 147,972 184,965 246,620 369,930 and 739,860, with no remainder.
Since 739,860 cannot be divided by just 1 and 739,860, it is not a prime number.