A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 306900 can be evenly divided by 1 2 3 4 5 6 9 10 11 12 15 18 20 22 25 30 31 33 36 44 45 50 55 60 62 66 75 90 93 99 100 110 124 132 150 155 165 180 186 198 220 225 275 279 300 310 330 341 372 396 450 465 495 550 558 620 660 682 775 825 900 930 990 1,023 1,100 1,116 1,364 1,395 1,550 1,650 1,705 1,860 1,980 2,046 2,325 2,475 2,790 3,069 3,100 3,300 3,410 4,092 4,650 4,950 5,115 5,580 6,138 6,820 6,975 8,525 9,300 9,900 10,230 12,276 13,950 15,345 17,050 20,460 25,575 27,900 30,690 34,100 51,150 61,380 76,725 102,300 153,450 and 306,900, with no remainder.
Since 306,900 cannot be divided by just 1 and 306,900, it is not a prime number.