lib/numb/factorial.rb in numb-0.170.0 vs lib/numb/factorial.rb in numb-0.181.0

@@ -12,6 +12,18 @@
       else
         return d.factorial == self
       end
     end
   end
+
+  def factorial_of?
+    return false unless factorial?
+    return 1 if self == 1
+    pfacts = primaries
+    divisors.sort.take_while.with_index{|d,i| d == i.succ}.reverse_each do |d|
+      pfacts.all? do |b, e|
+        (1..Math.log(d,b)).map{|k| Rational(d, b**k).floor}.reduce(:+) == e
+      end and return d
+    end
+    nil
+  end
 end