Q: Is 21,661 a Prime Number?
A: Yes, 21,661 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 21661 can be evenly divided by 1 and 21,661, with no remainder.
Since 21,661 can be divided by just 1 and 21,661, it is a prime number.