An iPhone that is compatible with Verizon has been rumored for a long time, and according to a recent survey, there’s demand among Verizon customers for the Apple device.

“According to our [Alphawise U.S. consumer iPhone survey], there is substantial pent up iPhone demand within the Verizon installed base as 16.8 percent of Verizon subscribers said they are very likely to purchase an iPhone if offered on the Verizon Network, said Morgan Stanley analyst Katy Huberty to HotHardware. This 16.8 percent is higher than AT&T subscriber s 14.6 percent extreme interest in the current AT&T iPhone, and well above the overall iPhone extreme interest of 7.5 percent.”

That may be good news for Apple, since Rodman Renshaw analyst Ashok Kumar says that the company is looking to increase its production rate by 25 percent to 4 million a month. Kumar says to TheStreet this is being done to prepare a Verizon iPhone for as early as November, though some think the move is simply to ramp up in production of the anticipated iPhone 4G.