I can see that penTlak Subvocalization in Flash Anzan asked similar question, but during past week i found that turning on music or humming distract me.
I can think non-verbally and if i see 5 digits or easy-to-spot pattern I do not subvocalize. But if anything is longer or complex I start to read and often make a mistake (or for 9 digit number I don’t find enough time to read. I use mostly Number blink 4 for training and next number 2 for pure entertainment.
Partial solution seem to be training to spot such patterns, or extend my list of number-real life occurrence relations (I know there are other number memory systems, but this one seem to be most natural for me) or somehow “improve” my number-color synesthesia. But do you have any other ideas?