A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 757120 can be evenly divided by 1 2 4 5 7 8 10 13 14 16 20 26 28 32 35 40 52 56 64 65 70 80 91 104 112 128 130 140 160 169 182 208 224 260 280 320 338 364 416 448 455 520 560 640 676 728 832 845 896 910 1,040 1,120 1,183 1,352 1,456 1,664 1,690 1,820 2,080 2,240 2,366 2,704 2,912 3,380 3,640 4,160 4,480 4,732 5,408 5,824 5,915 6,760 7,280 8,320 9,464 10,816 11,648 11,830 13,520 14,560 18,928 21,632 23,660 27,040 29,120 37,856 47,320 54,080 58,240 75,712 94,640 108,160 151,424 189,280 378,560 and 757,120, with no remainder.
Since 757,120 cannot be divided by just 1 and 757,120, it is not a prime number.