function is_Int(num) {  
    
   if (typeof num !== 'number')  
       return false;   
    
  return !isNaN(num) &&   
         parseInt(Number(num)) == num &&   
         !isNaN(parseInt(num, 10));  
}  
console.log(is_Int(23));  
console.log(is_Int(4e2));  
console.log(is_Int(NaN));  
console.log(is_Int(23.75));  
console.log(is_Int(-23));