Q: Is 21,721 a Prime Number?
A: No, 21,721 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 21721 can be evenly divided by 1 7 29 107 203 749 3,103 and 21,721, with no remainder.
Since 21,721 cannot be divided by just 1 and 21,721, it is not a prime number.