Q: Is 21,691 a Prime Number?
A: No, 21,691 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 21691 can be evenly divided by 1 109 199 and 21,691, with no remainder.
Since 21,691 cannot be divided by just 1 and 21,691, it is not a prime number.