I found this on the Internet and would like to make it work.
I placed the formula in cell B1 and the number to be examined in A1 however
it evaluates primes and non-primes as TRUE.
Obviously, I have done something wrong.
Can anyone steer me correctly?
POWER FORMULA TECHNIQUE
by Bob Umlas
This array formula returns TRUE if the number in cell A1 is a prime number.
Use it as a conditional formatting formula, with A1 as the active cell
in the selection to be formatted.
Here's how Bob's amazing formula works. In a nutshell, the number is
divided by all potential prime factors, and the resulting array is tested
to see whether it contains a whole number. If is does, you have a prime
number. A limitation of this formula is that it cannot test numbers that
are greater than 65535^2. This is due to the array size constraint in