sun-synodic

This web page verifies that The Sun's synodic rotation period = 26.44803 Earth days.

The Sun's (sidereal) rotation period = 24.66225 Earth days. To verify this, look at the table below, scanned from The Planetary Scientist's Companion, by Lodders and Fegley, 1998, Oxford University Press, Table 2.4 page 87.  

The Earth's orbital period = 365.25636 Earth days. To verify this, look at the following table, scanned from the book Movement and Rhythms of The Stars, by Joachim Schultz, published by Floris Books, Anthroposophical Press, 1986, page 222, Table 4.5

The Sun’s synodic rotation period = 1 ÷ [(1 ÷ 24.66225) MINUS (1 ÷ 365.25636)] = 26.44803 Earth days.