Q: Is 643,921 a Prime Number?
A: No, 643,921 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 643921 can be evenly divided by 1 379 1,699 and 643,921, with no remainder.
Since 643,921 cannot be divided by just 1 and 643,921, it is not a prime number.