Name of the hash algorithms and create an unhash function
EDIT - Per the helpful comments, this question involves a sort of broken base19 conversion with redundant characters from t through z.  As such the below does not reverse for any letters after 's'.  It could be fixed but I presume the question is just an intellectual exercise of some kind anyway.  It obviously is NOT a hash, nor is it an efficient coding system, snugly fitting 8 characters in a less than handy 34 bits.
From my rather layman point-of-view, it was difficult to initially spot as a base19 conversion due to the fact it's backwards (we treat the initial string as base19) and because of the way it multiplies 19 in a loop rather than explicitly $19^i$ (yeah I know...).

To reverse up to 's':
$61752 \mod 19 = 2$
We then take the rounded down result of 61752/19
Were left with $3250 \mod 19 = 1$
We then take the rounded down result of 3250/19
Were left with $171 \mod 19 = 0$
Here it is in Javascript
function rehash(str){
const letters = &quot;abcdefghijklmnopqrstuvwxyz&quot;;var out=&quot;&quot;;

while (str&gt;9) {
  out = letters.charAt(str%19) + out;
  str=Math.floor(str/19)
}
return out}