pass a variable in a array but error show NaN

pass a variable in a array but error show NaN

i am trying to pass a variable in a array but faild. it shows me NaN
var tatatat3;
tatatat3 = '';
var seprt;
seprt = '';
$.each( arrayvalueH, function( k, j ) {
if(j == undefined) return ;
//alert( k + ": " + j );
qtyxxx = $( "#qty"+k ).val()
tatatat3 = '"'+qtyxxx+'"'+seprt+tatatat3;
seprt = ',';
});
alert(tatatat3);
//console.log(tatatat3);
var somearray = [tatatat3];
alert(Math.min.apply(Math,somearray));
problem is i have tatatat3 = '2','1' value. but when i pass
Math.min.apply(Math,somearray) its alert me NaN. but if i pass Manual
'2','1' its alert me minimum value. i dont know where is the problem