The Biggest Number in the Universe

Nesta asks her next door neighbour for a number, any number, as long as it is big and impressive. The mathematician is not interested in helping to begin with but in the end he relents and lends Nesta 8,888,888,888 - a very impressive number indeed. But only on the understanding that she look after it and doesn't take it out of her pocket until she reaches school. But Nesta does...