BigInteger exp = new BigInteger("SOME BIG NUMBER", 10); 
            BigInteger n = new BigInteger("OTHER BIG NUMBER", 10); 
            BigInteger integer3 = new BigInteger(str.Substring(1), 0x24); 
            byte[] bytes = integer3.modPow(exp, n).getBytes(); 
            ASCIIEncoding encoding = new ASCIIEncoding(); 
            return new string(encoding.GetChars(bytes));

# Calculate the bit-width of cells on this system. 
 
sub count_bits { 
    my $i = 0; 
    my $q = ~0x0;      # Set all bits 
    while ( $q ) {     # All shifted out? 
        $q = $q << 1;  # Shift left 
        $i++;          # Accum shifts 
    } 
    return $i;         # Return bit-width 
} 
 
my $bits    = count_bits;       # System bit-width. 
my $cells   = int( $bits / 8 ); # max bytes in array 
my $mask    = ~0x0;             # Full mask = 0xF* 
my $top_bit = ~( $mask >> 1 );  # High mask = 0x80* 
 
########################## 
# END N-BIT SYSTEM CHECK # 
########################## 
 
# Convert a BigInt to an array. 
sub bint_to_array { 
  my $quo = shift; 
  my $msk = Math::BigInt->new($mask); 
  my @cls; 
  until ( $quo->is_zero() ) { 
    my $rem = $quo->copy();      # Lest modify ruin. 
    $rem->band($msk);            # REM = LSC 
    $quo->brsft($bits);          # QUO = Cells above 
    unshift @cls, $rem->bstr();  # Keep remainder 
  } 
  return @cls; 
} 
 
# Convert an array to a BigInt. 
sub array_to_bint { 
    my @cls = @_; 
    my $out = Math::BigInt->new(0); 
    my $i = 0; 
    while ( @_ ) { 
        my $lsc = Math::BigInt->new( pop @_ );  # LSC 
        $lsc->blsft($bits * $i);                # Shift up 
        $out->bior($lsc);                       # OR to LSC 
        ++$i; 
    } 
    return $out; 
}

my $string = "f4eoy18ien92q667yex54u6xqyd2u6e2j0kjkvtesj4gcbkij6yq93ms7kx4yzxx0gdmj9vrhk7yns371ormeg5j44jkm727tg3"; 
my @ascii  = unpack("C*", $string); 
my $x = array_to_bint(@ascii); 
 
my $exp = "1699226779513586444311853417832813053444275415713267420973354241696037822738978485422119265005494628039077923965408489035118957525416966246759228390003017"; 
my $n = "8496133897567932221559267089164065267221377078566337104866771208480189113695076911576868324903413008512741498700587851315525414979963642608998181269527941"; 
 
$x->bmodpow($exp,$n); 
 
my @a = bint_to_array   ($x); 
 
my $z; 
foreach $z (@a) 
{ 
  print "arg: $z\n"; 
}

#!/usr/bin/perl 
 
use Math::BigInt; 
use Math::Base36 ':all'; 
 
my $b36 = 'f4eoy18ien92q667yex54u6xqyd2u6e2j0kjkvtesj4gcbkij6yq93ms7kx4yzxx0gdmj9vrhk7yns371ormeg5j44jkm727tg3'; 
my $exp = Math::BigInt->new('1699226779513586444311853417832813053444275415713267420973354241696037822738978485422119265005494628039077923965408489035118957525416966246759228390003017');  
my $n = Math::BigInt->new('8496133897567932221559267089164065267221377078566337104866771208480189113695076911576868324903413008512741498700587851315525414979963642608998181269527941');  
  
$x = Math::BigInt->new(decode_base36($b36)); 
$x->bmodpow($exp,$n);  
print "\nAns:  ".$x->bstr()."\n\n";

$ ./big.pl  
 
Ans:  8903715056186744936505705128241 
 
$

@nums = split(//,$x->bstr());

$str = encode_base36($x);

public BigInteger(string value, int radix)