diff --git a/src/factor.c b/src/factor.c
index 2784320..b57b61c 100644
--- a/src/factor.c
+++ b/src/factor.c
@@ -502,6 +502,12 @@ Print the prime factors of each specified integer NUMBER.  If none\n\
 are specified on the command line, read them from standard input.\n\
 \n\
 "), stdout);
+#ifdef HAVE_GMP
+      printf (_("Compiled with big numbers support using gmp version %s\n\n"), gmp_version);
+#else
+      printf (_("Compiled without big numbers support: maximum input size supported is %lu\n\n"), UINTMAX_MAX);
+#endif
+
       fputs (HELP_OPTION_DESCRIPTION, stdout);
       fputs (VERSION_OPTION_DESCRIPTION, stdout);
       emit_ancillary_info ();