Add BigInt type of data to your custom entity

To have integer go to BigInt type you will need to use setSettings in your BaseFieldDefinition for your custom entity, with this you will have space for 19 digits numbers, with unsigned property making this all positive numbers.

     $fields['volume'] = BaseFieldDefinition::create('integer')
      ->setLabel(t('Volume'))
      ->setDescription(t('Volume of the Currency'))
      ->setSettings([
           'unsigned' => true,
           'size' => 'big'
         ])
      ->setDisplayOptions('form', array(
        'type' => 'number',
        'settings' => array(
          'display_label' => TRUE,
        ),
      ))
     ->setDisplayOptions('view', array(
        'label' => 'hidden',
        'type' => 'number_integer',
      ))
      ->setDisplayConfigurable('form', TRUE)
      ->setRequired(TRUE);