Q: Is 621,721 a Prime Number?
A: Yes, 621,721 is a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 621721 can be evenly divided by 1 and 621,721, with no remainder.
Since 621,721 can be divided by just 1 and 621,721, it is a prime number.