# [Pari/GP], 37 bytes

 a->[if(x<2,-1,x/divisors(x)[2])|x<-a]

[Try it online!][TIO-jgox4fmq]

[Pari/GP]: http://pari.math.u-bordeaux.fr/
[TIO-jgox4fmq]: https://tio.run/##LYrBCgIxDER/JeyphRSbxIPCuj9SeihIpSBauiIV/PeaXTzMMPNmamrF3erIcBnJLaFk02dGR9gP1/Iu67OtptvA0X777FIcqdb7xyRwC9RWHi@N01YmyCZZixACITCCIBwRyKsUkESdyGvl3YSEN65Bz/uL5ETsz38oMdrxAw "Pari/GP – Try It Online"