Q: Is 21,391 a Prime Number?
A: Yes, 21,391 is a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 21391 can be evenly divided by 1 and 21,391, with no remainder.
Since 21,391 can be divided by just 1 and 21,391, it is a prime number.