Q: Is 21,728 a Prime Number?
A: No, 21,728 is not a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 21728 can be evenly divided by 1 2 4 7 8 14 16 28 32 56 97 112 194 224 388 679 776 1,358 1,552 2,716 3,104 5,432 10,864 and 21,728, with no remainder.
Since 21,728 cannot be divided by just 1 and 21,728, it is not a prime number.