Thread: Exit status 15 View Single Post 2020-10-15, 08:49 #5 kruoli   "Oliver" Sep 2017 Porta Westfalica, DE 1111011102 Posts Yes! If it finds the number itself: Code: ~$echo 2047 | ecm -one 1000 GMP-ECM 7.0.4 [configured with GMP 6.2.0, --enable-asm-redc] [ECM] Input number is 2047 (4 digits) Using B1=1000, B2=51606, polynomial x^1, sigma=1:2307810929 Step 1 took 1ms ********** Factor found in step 1: 2047 Found input number N ~$ echo $? 8 If it finds a factor and the cofactor is prime (maybe PRP): Code: ~$ echo 2047 | ecm -one 1 GMP-ECM 7.0.4 [configured with GMP 6.2.0, --enable-asm-redc] [ECM] Input number is 2047 (4 digits) Using B1=1, B2=12, polynomial x^1, sigma=1:309160743 Step 1 took 0ms Step 2 took 0ms ********** Factor found in step 2: 23 Found prime factor of 2 digits: 23 Prime cofactor 89 has 2 digits ~$echo$? 14 If it finds a factor and the cofactor is composite: Code: ~$echo '2*(2^2047-1)' | ecm -one 1 GMP-ECM 7.0.4 [configured with GMP 6.2.0, --enable-asm-redc] [ECM] Input number is 2*(2^2047-1) (617 digits) ********** Factor found in step 1: 2 Found prime factor of 1 digits: 2 Composite cofactor (2*(2^2047-1))/2 has 617 digits ~$ echo \$? 6 I'd have to look into the code if there are other possibilities.  