☙

zetta-

In SI, the decimal multiplier prefix that signifies 10²¹ of the unit modified (a sextillion, in the American style of large numbers, or one thousand trillion, continental style). Symbol, Z.

It was proposed by the CIPM in 1990, and adopted by the 19ᵗʰ CGPM in 1991. For the origin of the term see zepto-.

Comptes Rendus des Séances de la Conférence Generale des Poids et Mesures, 185.

T. J. Quinn.
News from the BIPM.
Metrologia, volume 29, no. 1, page 3 (1992).