No word yet on exactly how many Apple (AAPL) shares Icahn holds, or what Cook’s response was to Icahn’s overture. Apple stock had been relatively flat before Icahn’s tweets, but by 2:50pm was up more than $17 per share (3.66%). For the year, Apple is down more than 11% — causing some longtime shareholders to believe the company’s best growth is behind it.

Icahn is no stranger to technology, based on his past Motorola experience and his current attempts to gain control of Dell Inc. (DELL). He also has generated more than $1 billion in paper returns from his 2012 investment at Netflix — buying at just $58 per share, compared to the company’s current $261 per share mark.

Perhaps most relevant is Icahn’s 16.03% stake in Nuance Communications (NUAN), which Apple uses for its Siri voice recognition feature.

Apple followed Icahn’s tweet by issuing the following statement: “We appreciate the interest and investment of all our shareholders. Tim had a very positive conversation with Mr. Icahn today.”

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