Fishhook cactus

Quoting from Wikipedia: Fishhook cactus,

Fishhook cactus is a common name for any hook-spined species of the genera Mammillaria, Echinomastus or Sclerocactus. They are small cacti, usually growing up to 6-7 inches (20 cm) high, and are shaped similar to a barrel cactus. They are not to be confused with the fishhook barrel cactus (Ferocactus wislizenii) of the Sonoran and Chihuahuan Deserts. The Fishhook cactus is a large category of around 150 species.

You might get any of these cactus confused. This particular fishhook cactus is likely a Sclerocactus. But you are welcome to leave your opinion as a comment. They are all so similar. It is unusual to see some types of cactus growing outdoors except in the lower deserts. The Southwest corner of Utah drops to below 2000' in some locations. St. George, Utah, where this particular cactus was growing is about 2700' above sea level. It is still so cold, at times, in St. George that if not cared for, the cactus will freeze.