A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6377550 can be evenly divided by 1 2 3 5 6 10 15 17 25 30 34 41 50 51 61 75 82 85 102 122 123 150 170 183 205 246 255 305 366 410 425 510 610 615 697 850 915 1,025 1,037 1,230 1,275 1,394 1,525 1,830 2,050 2,074 2,091 2,501 2,550 3,050 3,075 3,111 3,485 4,182 4,575 5,002 5,185 6,150 6,222 6,970 7,503 9,150 10,370 10,455 12,505 15,006 15,555 17,425 20,910 25,010 25,925 31,110 34,850 37,515 42,517 51,850 52,275 62,525 75,030 77,775 85,034 104,550 125,050 127,551 155,550 187,575 212,585 255,102 375,150 425,170 637,755 1,062,925 1,275,510 2,125,850 3,188,775 and 6,377,550, with no remainder.
Since 6,377,550 cannot be divided by just 1 and 6,377,550, it is not a prime number.