How many zeros in one pentillion?

Answer 1

To get around the confusion between the US and European use of billion (thousand million or million million) and higher numbers new names, based on Greek roots, were proposed. In many countries the European names have now been dropped in favour of the US names.

Pentillion was the name proposed for quadrillion = 1015

It would have had 15 zeros if the name had caught on.

Answer 2

There's 15 zeros in one pentillion.