A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1748736 can be evenly divided by 1 2 3 4 6 8 9 11 12 16 18 22 23 24 27 32 33 36 44 46 48 54 64 66 69 72 88 92 96 99 108 128 132 138 144 176 184 192 198 207 216 253 256 264 276 288 297 352 368 384 396 414 432 506 528 552 576 594 621 704 736 759 768 792 828 864 1,012 1,056 1,104 1,152 1,188 1,242 1,408 1,472 1,518 1,584 1,656 1,728 2,024 2,112 2,208 2,277 2,304 2,376 2,484 2,816 2,944 3,036 3,168 3,312 3,456 4,048 4,224 4,416 4,554 4,752 4,968 5,888 6,072 6,336 6,624 6,831 6,912 8,096 8,448 8,832 9,108 9,504 9,936 12,144 12,672 13,248 13,662 16,192 17,664 18,216 19,008 19,872 24,288 25,344 26,496 27,324 32,384 36,432 38,016 39,744 48,576 52,992 54,648 64,768 72,864 76,032 79,488 97,152 109,296 145,728 158,976 194,304 218,592 291,456 437,184 582,912 874,368 and 1,748,736, with no remainder.
Since 1,748,736 cannot be divided by just 1 and 1,748,736, it is not a prime number.