The number of subscribers to Kakao Pay Securities, the brokerage arm of mobile messenger giant Kakao, surpassed the 5 million mark as of July, 17 months since its inception, the company said Friday.

The number is equivalent to one-fifth of the 28 million South Koreans who are economically active, it added.

According to the Korea Financial Investment Association, the number of accounts used for public offering funds via Kakao Pay Securities surpassed 2.1 million as of June.

The number of subscribers using easy-to-use investment services such as “spare change investment” and “cash back investment” surged more than 500 percent from last year, Kakao Pay Securities said.

The company plans to launch a mobile trading system this year that will facilitate the trading of stocks listed on local markets as well as overseas, officials said without elaborating on the exact timeline.

Investors with existing Kakao Pay accounts can start trading without having to open new accounts, they added.