FlexPro’s best-exact-n FFT uses four different FFT algorithms to minimizes computation time based on the size of the input data. If the data size is a power of 2, the FFT Radix 2 algorithm is used. If not and the size is included in the prime-factor set, then the Prime Factor procedure is used. Otherwise, the Mixed Radix algorithm is used if the largest prime = 521. This produces the fastest possible exact-n FFT.
See also FlexPro Help – FFT Algorithms