Q: Is 21,663 a Prime Number?
A: No, 21,663 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 21663 can be evenly divided by 1 3 9 29 83 87 249 261 747 2,407 7,221 and 21,663, with no remainder.
Since 21,663 cannot be divided by just 1 and 21,663, it is not a prime number.