title: insert query is giving ORA-01722: invalid number error
body: <p>I created a stock table with the below query </p>
  
  <pre><code>CREATE TABLE stock
    (
      product_id REFERENCES product ,
      product_name REFERENCES product ,
      color    VARCHAR2(20) ,
      memory   VARCHAR2(20) ,
      in_stock NUMBER(3)
    );
  </code></pre>
  
  <p>I tried to insert a row into this using the below query:</p>
  
  <pre><code>insert into stock values(8881,'Nexus 4','Black','2GB-16GB',3);
  </code></pre>
  
  <p>and it is giving <strong>ORA-01722: invalid number error</strong> , I know why the error comes , but I can't figure out what wrong I have done</p>
  
  <p>product table : </p>
  
  <pre><code>product_id ..number , product_name .. varchar2
  </code></pre>
  
  <p>adding a pic </p>
  
  <p><a href="https://i.stack.imgur.com/IjLVC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IjLVC.png" alt="enter image description here"></a></p>