* Shire accepts Abbvie takeover offer
* Citigroup to pay $7 bln to settle investigation
* Futures up: Dow 57 pts, S&P 6.75 pts, Nasdaq 18.25 pts
NEW YORK, July 14 (Reuters) - U.S. stock index futures rose on Monday, after the S&P 500 suffered its worst weekly decline since April and the latest flurry of merger activity.
* London-listed drugmaker Shire Plc succumbed to an increased 31 billion pounds ($53 billion) takeover offer from Abbvie Inc, ending a long-running courtship largely motivated by tax rates. U.S.-listed shares of Shire rose 2.4 percent to $255.10 while Abbvie shed 0.7 percent to $54.56 in premarket trade.
* Generic drugmaker Mylan Inc said it would buy Abbott Laboratories' specialty and branded generics business outside the United States in an all-stock transaction valued at about $5.3 billion. Mylan shares jumped 9.6 percent to $55 before the opening bell. Abbot shares rose 2.3 percent in light premarket trade.
* Citigroup Inc shares rose 1.4 percent to $47.65 in premarket after it agreed to pay $7 billion to settle a U.S. government investigation into mortgage-backed securities the bank sold in the run-up to the 2008 financial crisis. The bank is also expected to post earnings on Monday.
* Earnings season will pick up speed this week, with 50 S&P 500 components scheduled to report. S&P 500 profits are seen growing 6.1 percent in the second quarter, according to Thomson Reuters data, down from the 8.4 percent growth forecast at the start of April. Revenue is seen up 3 percent.
* Analysts are looking to earnings for confirmation that the economy recovered in the second quarter from the impact of a harsh winter in order to justify current stock prices.
* S&P 500 e-mini futures were up 6.75 points and fair value - a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract - indicated a higher open. Dow Jones industrial average e-mini futures rose 57 points and Nasdaq 100 e-mini futures added 18.25 points.
* Exelixis shares surged 11.2 percent to $3.70 after the company's experimental skin cancer treatment being developed with Roche helped people with an advanced form of skin cancer live longer without their disease worsening when used in combination with another treatment, the companies said.
* European shares rose, boosted by M&A activity in the pharmaceutical sector and rallying from near two-month lows after their biggest weekly loss in four months.
* Asian shares rose as investors put aside concerns about euro zone banks and looked forward to corporate earnings and a raft of global economic events, including testimony from the head of the Federal Reserve.
(Reporting by Chuck Mikolajczak; Editing by Chizu Nomiyama)