Is possible to concatenate integers?
If you are reading from the analog pins then the values are 10 bits (not 8 as suggested above).  Are you looking at concatenating 2 10 bit numbers or 2 16 bit numbers or are you using a zero or duo in which case they could be 12 bit numbers.

In any case:

const int BITMASK = 0x3FF;  // 10 bits = 0x3FF, 12 = 0xFFF, 16 = 0xFFFF
const int BITWIDTH = 10;
long result = ((value1 &amp; BITMASK) &lt;&lt; BITWIDTH) | (value2 &amp; BITMASK);


I suspect it won't give you the answer you want, but...