A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7748000 can be evenly divided by 1 2 4 5 8 10 13 16 20 25 26 32 40 50 52 65 80 100 104 125 130 149 160 200 208 250 260 298 325 400 416 500 520 596 650 745 800 1,000 1,040 1,192 1,300 1,490 1,625 1,937 2,000 2,080 2,384 2,600 2,980 3,250 3,725 3,874 4,000 4,768 5,200 5,960 6,500 7,450 7,748 9,685 10,400 11,920 13,000 14,900 15,496 18,625 19,370 23,840 26,000 29,800 30,992 37,250 38,740 48,425 52,000 59,600 61,984 74,500 77,480 96,850 119,200 149,000 154,960 193,700 242,125 298,000 309,920 387,400 484,250 596,000 774,800 968,500 1,549,600 1,937,000 3,874,000 and 7,748,000, with no remainder.
Since 7,748,000 cannot be divided by just 1 and 7,748,000, it is not a prime number.