A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3306204 can be evenly divided by 1 2 3 4 6 9 11 12 18 22 23 27 33 36 44 46 54 66 69 92 99 108 121 132 138 198 207 242 253 276 297 363 396 414 484 506 594 621 726 759 828 1,012 1,089 1,188 1,242 1,331 1,452 1,518 2,178 2,277 2,484 2,662 2,783 3,036 3,267 3,993 4,356 4,554 5,324 5,566 6,534 6,831 7,986 8,349 9,108 11,132 11,979 13,068 13,662 15,972 16,698 23,958 25,047 27,324 30,613 33,396 35,937 47,916 50,094 61,226 71,874 75,141 91,839 100,188 122,452 143,748 150,282 183,678 275,517 300,564 367,356 551,034 826,551 1,102,068 1,653,102 and 3,306,204, with no remainder.
Since 3,306,204 cannot be divided by just 1 and 3,306,204, it is not a prime number.