Thanks Laurel . Have added another loop to check if the number is divisble by odd numbers and finally add to the number to the list oncethe number becomes greater than 2 

#!/usr/bin/perl
use warnings;
use strict;
########

sub prime_factors {
    my $num = shift;
    my @primes = ();
    my $max = sqrt($num);
    while ($num % 2 == 0) {
        push @primes, 2;
        $num /= 2;
    }

    foreach (my $i = 3; $i <= $max; $i += 2) {
        if ($num % $i == 0) {
            push @primes, $i;
            $num /= $i;
                $max = sqrt($num);
             redo;
        }
     }

     if ($num > 2) {
        push @primes, $num;
     }

     return @primes;
}

foreach my $n ( (20, 48, 96, 7, 69, 33, 54, 13195,  600851475143, 2147
+483647, 29474100, 3217491003, 27000) ) {
    my @result = prime_factors($n);
    print "Number: $n , Prime_Factors: => @result", "\n";
}

$time ./primes.pl
Number: 20 , Prime_Factors: => 2 2 5
Number: 48 , Prime_Factors: => 2 2 2 2 3
Number: 96 , Prime_Factors: => 2 2 2 2 2 3
Number: 7 , Prime_Factors: => 7
Number: 69 , Prime_Factors: => 3 23
Number: 33 , Prime_Factors: => 3 11
Number: 54 , Prime_Factors: => 2 3 3 3
Number: 13195 , Prime_Factors: => 5 7 13 29
Number: 600851475143 , Prime_Factors: => 71 839 1471 6857
Number: 2147483647 , Prime_Factors: => 2147483647
Number: 29474100 , Prime_Factors: => 2 2 3 3 5 5 32749
Number: 3217491003 , Prime_Factors: => 3 32749 32749
Number: 27000 , Prime_Factors: => 2 2 2 3 3 3 5 5 5

real    0m0.015s
user    0m0.009s
sys    0m0.004s

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In reply to Re^8: Avoid keeping larger lists in Memory by pr33
in thread Avoid keeping larger lists in Memory by pr33

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