Gymnocalycium buenekeri

Gymnocalycium buenekeri have great pink flowers and (usually) five ribbed appearance, and good, yellow spines. It can clump and is quick to grow.
Cultivation and Propagation: Very easy to grow, these plants offer no cultivation difficulties. Summer grower needs moderate to copious waterings in summer. Quite frost resistant if kept dry in winter -4° C. Feed with a high potassium fertilizer in summer. Sun Exposure: Full sun to light shade.

Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz