What was the name of the 400 star gods who were the brothers of Huitzilopochtli?

The 400 star gods who were brothers of Huitzilopochtli were the Centzon Huitznahua. Their name is also written Centzonhuītznāhua or, in plural form, Centzon Huītznāuhtin.

In Mexica mythology, the Centzon Huitznahua were the gods of the southern stars and children of Coatlicue. Their sister was Coyolxauhqui, associated with the moon. When Coatlicue became mysteriously pregnant after finding a ball of feathers, her children regarded the pregnancy as dishonorable and planned to kill her.

Huitzilopochtli then emerged from the womb fully grown and armed. He defeated the rebellious brothers, while Coyolxauhqui was beheaded and thrown down Coatepec, the sacred Serpent Mountain. The brothers fled and became scattered across the sky, explaining their association with the southern stars.

“Four hundred” is not necessarily a literal census. In Nahuatl religious language, centzon could express an innumerable multitude. A common mix-up is the Centzon Huitznahua versus the Centzon Mimixcoa, another group of four-hundred star beings associated with the northern sky.