(12C) Check if given number is Prime Number or not

[Thomas Klemm]

(09-11-2018 05:42 AM)Gamo Wrote:  Is this another rounding problem on the 12C ?

Yes. Since the real HP-12C uses 10 digits: 9,000,000,001 ÷ 2 = 4,500,000,001.
The fractional part of this number is 0 and the program jumps to line 29:

Code:

04 RCL 0
05 2
06 STO 2
07 ÷
08 FRAC
09 X=0?
10 GTO 29

And thus the program tells you erroneously that this number is divisible by 2.

HTH
Thomas