🚀 go-pugleaf

I am reading an old paper by Tompa that describes Blum's protocol for
flipping coins by telephone.  The first thing the verifier must do is
verify that a very large (hundreds of digits) number has at least two
distinct prime factors (i.e., that the number is not a prime power).
Tompa gives no hint how to do this and I haven't been able to find anyone
else who knows.  I'd very much appreciate it if someone could explain
how it's done or point me to a paper somewhere...