Perfect numbers: Difference between revisions

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→‎optimized using only even numbers: added a factoid. -- ~~~~
m (→‎optimized using digital root: added a factoid. -- ~~~~)
m (→‎optimized using only even numbers: added a factoid. -- ~~~~)
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===optimized using only even numbers===
This REXX version uses the fact that all ''known'' perfect numbers are ''even''.
<lang rexx>/*REXX program tests if a number (or a range of numbers) is/are perfect.*/
parse arg low high . /*obtain the specified number(s).*/