A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1634760 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 18 19 20 24 30 36 38 40 45 57 60 72 76 90 95 114 120 152 171 180 190 228 239 285 342 360 380 456 478 570 684 717 760 855 956 1,140 1,195 1,368 1,434 1,710 1,912 2,151 2,280 2,390 2,868 3,420 3,585 4,302 4,541 4,780 5,736 6,840 7,170 8,604 9,082 9,560 10,755 13,623 14,340 17,208 18,164 21,510 22,705 27,246 28,680 36,328 40,869 43,020 45,410 54,492 68,115 81,738 86,040 90,820 108,984 136,230 163,476 181,640 204,345 272,460 326,952 408,690 544,920 817,380 and 1,634,760, with no remainder.
Since 1,634,760 cannot be divided by just 1 and 1,634,760, it is not a prime number.