Q: Is 639,664 a Prime Number?
A: No, 639,664 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 639664 can be evenly divided by 1 2 4 8 16 39,979 79,958 159,916 319,832 and 639,664, with no remainder.
Since 639,664 cannot be divided by just 1 and 639,664, it is not a prime number.