"numero difettivo" meaning in Italian

{
  "forms": [
    {
      "form": "numeri difettivi",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "m"
      },
      "expansion": "numero difettivo m (plural numeri difettivi)",
      "name": "it-noun"
    }
  ],
  "lang": "Italian",
  "lang_code": "it",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Italian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "it",
          "name": "Mathematics",
          "orig": "it:Mathematics",
          "parents": [
            "Formal sciences",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "defective number"
      ],
      "id": "en-numero_difettivo-it-noun-~O4~EVW3",
      "links": [
        [
          "mathematics",
          "mathematics"
        ],
        [
          "defective number",
          "defective number"
        ]
      ],
      "raw_glosses": [
        "(mathematics) defective number"
      ],
      "tags": [
        "masculine"
      ],
      "topics": [
        "mathematics",
        "sciences"
      ],
      "wikipedia": [
        "it:numero difettivo"
      ]
    }
  ],
  "word": "numero difettivo"
}

{
  "forms": [
    {
      "form": "numeri difettivi",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "m"
      },
      "expansion": "numero difettivo m (plural numeri difettivi)",
      "name": "it-noun"
    }
  ],
  "lang": "Italian",
  "lang_code": "it",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Italian countable nouns",
        "Italian entries with incorrect language header",
        "Italian lemmas",
        "Italian masculine nouns",
        "Italian multiword terms",
        "Italian nouns",
        "it:Mathematics"
      ],
      "glosses": [
        "defective number"
      ],
      "links": [
        [
          "mathematics",
          "mathematics"
        ],
        [
          "defective number",
          "defective number"
        ]
      ],
      "raw_glosses": [
        "(mathematics) defective number"
      ],
      "tags": [
        "masculine"
      ],
      "topics": [
        "mathematics",
        "sciences"
      ],
      "wikipedia": [
        "it:numero difettivo"
      ]
    }
  ],
  "word": "numero difettivo"
}