Q: Is 21,399 a Prime Number?
A: No, 21,399 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 21399 can be evenly divided by 1 3 7 21 1,019 3,057 7,133 and 21,399, with no remainder.
Since 21,399 cannot be divided by just 1 and 21,399, it is not a prime number.