Q: Is 21,945 a Prime Number?
A: No, 21,945 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 21945 can be evenly divided by 1 3 5 7 11 15 19 21 33 35 55 57 77 95 105 133 165 209 231 285 385 399 627 665 1,045 1,155 1,463 1,995 3,135 4,389 7,315 and 21,945, with no remainder.
Since 21,945 cannot be divided by just 1 and 21,945, it is not a prime number.