If ViaBTC doesn't allow you to withdraw that amount, it's probably because they have a min. withdrawal amount just like exchanges does.
You are right, Viabtc has a minimum withdrawal limit for coins and for Bitcoin, it is 0.001
BTC which explains why OP can't able to withdraw his 0.00052172
BTC.
ViaBTC minimum withdrawal limitActually it is not ViaBTC impeding me to withdraw, but Electrum. When I enter the amount, it tells me that it is too small.