An example of how to validate maxlength attribute for input type="number" and how to do not allow to put "e" symbol.

input_type_number.html

<input type="number"
  oninput="javascript: if (this.value.length > this.maxLength) this.value = this.value.slice(0, this.maxLength);"
  maxlength="6" required/>

<script>
  // do not allow to put "e" symbol
  $('input[type="number"]').on('keydown', function(e) {
    let keyCode = e.keyCode || e.which;
    
    if( keyCode == 69 ) 
    {
      return;
    }
  });
  
  // or
  
  $('input[type="number"]').on('keydown', function (e) {
    let  value = String.fromCharCode(e.keyCode);

    if( value === 'E' )
    {
        e.preventDefault();
    }
  });
</script>