Here is the best answer that I found for you on a Google search......Kirk Janowiak, M.S. (x 2) Biology & Ethology, Purdue University Answered Aug 15, 2015 The answer depends upon whether or not you accept Interphase as a phase of mitosis. I do not. I consider Interphase (as the name implies) the state that the cell is in between divisions; that is, the time the cell is going about doing its little cellular thing. If you think Interphase is part of mitosis, this is certainly the longest phase. But if you are like me and know that Interphase is the time of a normal cell's normal life and it is producing cell products, moving cell parts, and generally doing cellular activities, then Prophase is our winner. Prophase in mitosis is longer than metaphase, anaphase or telophase. A great deal of preparation for actual division takes place from early through late prophase, from spinning down the DNA/chromatin into chromosomes, to the dissolution of the nuclear membrane, to the initiation of spindle formation, movement of other cellular products to general areas within the cell, and many other tiny steps that get the DNA material protected and ready to be properly separated.
