This flower of Crassula argentea is actinomorphic (regular). This means that the flower has a radial symmetry it can be divided into two equal halves by two or more planes (5 here, shown by the yellow lines).
This flower is also typically 5-merous. The number of floral parts in each series is equal to five (a multiple of five).
Photo by K. R. Robertson and D. L. Nickrent of plants cultivated at the University of Illinois.