#PHP, 9 bytes, MAX INT (9223372036854775807)

echo ~0^1<<63; 

or

echo -1^1<<63; 

Set an int of all bits on (-1) then XOR it with an int of only the first bit on to flip the sign bit.

PHP, 9 bytes, MAX INT (9223372036854775807)

echo ~0^1<<63; 

or

echo -1^1<<63; 

Set an int of all bits on (-1) then XOR it with an int of only the first bit on to flip the sign bit.