A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1357620 can be evenly divided by 1 2 3 4 5 6 10 11 12 15 17 20 22 30 33 34 44 51 55 60 66 68 85 102 110 121 132 165 170 187 204 220 242 255 330 340 363 374 484 510 561 605 660 726 748 935 1,020 1,122 1,210 1,331 1,452 1,815 1,870 2,057 2,244 2,420 2,662 2,805 3,630 3,740 3,993 4,114 5,324 5,610 6,171 6,655 7,260 7,986 8,228 10,285 11,220 12,342 13,310 15,972 19,965 20,570 22,627 24,684 26,620 30,855 39,930 41,140 45,254 61,710 67,881 79,860 90,508 113,135 123,420 135,762 226,270 271,524 339,405 452,540 678,810 and 1,357,620, with no remainder.
Since 1,357,620 cannot be divided by just 1 and 1,357,620, it is not a prime number.