Q: Is 21,378 a Prime Number?
A: No, 21,378 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 21378 can be evenly divided by 1 2 3 6 7 14 21 42 509 1,018 1,527 3,054 3,563 7,126 10,689 and 21,378, with no remainder.
Since 21,378 cannot be divided by just 1 and 21,378, it is not a prime number.