TM4C1290NCPDT: Can i use a 26MHz input clock?

Currently we are using 13MHz clock as external input clock and configuring PLL core clock as 104MHz from that. But we are seeing 13MHz clock harmonics in the RF path as spur and we are working on the solutions to reduce that spur level. If it's ok to apply 26MHz to this controller, then we would not worry about that spur as it gets outside the RF in-band frequency.