A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7561400 can be evenly divided by 1 2 4 5 7 8 10 11 14 20 22 25 28 35 40 44 50 55 56 70 77 88 100 110 140 154 175 200 220 275 280 308 350 385 440 491 550 616 700 770 982 1,100 1,400 1,540 1,925 1,964 2,200 2,455 3,080 3,437 3,850 3,928 4,910 5,401 6,874 7,700 9,820 10,802 12,275 13,748 15,400 17,185 19,640 21,604 24,550 27,005 27,496 34,370 37,807 43,208 49,100 54,010 68,740 75,614 85,925 98,200 108,020 135,025 137,480 151,228 171,850 189,035 216,040 270,050 302,456 343,700 378,070 540,100 687,400 756,140 945,175 1,080,200 1,512,280 1,890,350 3,780,700 and 7,561,400, with no remainder.
Since 7,561,400 cannot be divided by just 1 and 7,561,400, it is not a prime number.