A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1058760 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 17 18 20 24 30 34 36 40 45 51 60 68 72 85 90 102 120 136 153 170 173 180 204 255 306 340 346 360 408 510 519 612 680 692 765 865 1,020 1,038 1,224 1,384 1,530 1,557 1,730 2,040 2,076 2,595 2,941 3,060 3,114 3,460 4,152 5,190 5,882 6,120 6,228 6,920 7,785 8,823 10,380 11,764 12,456 14,705 15,570 17,646 20,760 23,528 26,469 29,410 31,140 35,292 44,115 52,938 58,820 62,280 70,584 88,230 105,876 117,640 132,345 176,460 211,752 264,690 352,920 529,380 and 1,058,760, with no remainder.
Since 1,058,760 cannot be divided by just 1 and 1,058,760, it is not a prime number.