Q: Is 638,421 a Prime Number?
A: No, 638,421 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 638421 can be evenly divided by 1 3 7 21 43 49 101 129 147 301 303 707 903 2,107 2,121 4,343 4,949 6,321 13,029 14,847 30,401 91,203 212,807 and 638,421, with no remainder.
Since 638,421 cannot be divided by just 1 and 638,421, it is not a prime number.