perl -Mstrict -Mwarnings -le 'my $n = shift or die qq{Requires 1 number argument.}; my $o = $n; my @f = (); my $i = 2; while ( $n % $i == 0 ) { push @f, $i; $n /= $i; } $i++; while ( $n >= $i ) { while ( $n % $i == 0 ) { push @f, $i; $n /= $i; } if ( $n > $i ) { $i += 2; } } print $o, q{ = }, join q{*}, @f;'

##</code><code>##

$ for number in 3 31 314 3142 31416 314159 3141593 31415927 314159265 3141592654 31415926536 ; do time -p perl -Mstrict -Mwarnings -le 'my $n = shift or die qq{Requires 1 number argument.}; my $o = $n; my @f = (); my $i = 2; while ( $n % $i == 0 ) { push @f, $i; $n /= $i; } $i++; while ( $n >= $i ) { while ( $n % $i == 0 ) { push @f, $i; $n /= $i; } if ( $n > $i ) { $i += 2; } } print $o, q{ = }, join q{*}, @f;'  $number ; done
3 = 3
real 0.05
user 0.00
sys 0.04
31 = 31
real 0.04
user 0.00
sys 0.03
314 = 2*157
real 0.03
user 0.00
sys 0.03
3142 = 2*1571
real 0.03
user 0.01
sys 0.01
31416 = 2*2*2*3*7*11*17
real 0.03
user 0.00
sys 0.03
314159 = 314159
real 0.07
user 0.04
sys 0.04
3141593 = 7*13*19*23*79
real 0.03
user 0.00
sys 0.01
31415927 = 31*103*9839
real 0.03
user 0.01
sys 0.01
314159265 = 3*3*5*7*127*7853
real 0.03
user 0.03
sys 0.01
3141592654 = 2*139*2131*5303
real 0.03
user 0.00
sys 0.01
31415926536 = 2*2*2*3*3*436332313
real 47.17
user 47.03
sys 0.03