In the us, 1bln = 1000 million (1,000,000,000)
In the uk, although somewhat outdated, 1bln = 1 million x 1 million = 1 US-style trillion (1,000,000,000,000)
It scales up from there, too, I believe.
trillion is 1M^3, quadrillion 1M^4.
Thus, a THz to an old britisher sounds like 1,000,000,000,000,000,000