DUODECILLION

[duo.de.cil.lion] n, often attrib [L duodecim twelve + E -illion (as in million)] (1875): the figure 1 followed by 39 zeroes: the figure 1,000 followed by 12 groups of three zeroes; also, Brit: the figure 1 followed by 72 zeroes: one million to the 12th power