Q: Is 21,491 a Prime Number?
A: Yes, 21,491 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 21491 can be evenly divided by 1 and 21,491, with no remainder.
Since 21,491 can be divided by just 1 and 21,491, it is a prime number.