Climb a step to a prime
Python, 166 162 159 bytes
You guys are much better. This is what I used! (the algorithm that solved it calls this)

from primefac import*
def c(n):
 x=factorint(n)
 a=''
 for i in range(len(x)):
  l=min(x.keys())
  a+=str(l)
  if x[l]&gt;1:a+=str(x[l])
  x.pop(l)
 return int(a)