Q: Is 21,603 a Prime Number?
A: No, 21,603 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 21603 can be evenly divided by 1 3 19 57 379 1,137 7,201 and 21,603, with no remainder.
Since 21,603 cannot be divided by just 1 and 21,603, it is not a prime number.