title: Regex for at least a certain number of digits in a string
body: <p>When a user submits a form I need to make sure that the input contains at least a minimum number of digits. The problem is that I don't know what format the input will be in. The digits likely won't be in a row, and might be separated by letters, punctuation, spaces, etc. I don't care about the rest of the string.</p>
  
  <p>I'd like to check this with a RegularExpressionValidator but I'm not quite sure how to write the regex.</p>
  
  <p>I guess this would be similar to a phone number regex, but a phone number at least has some common formats.</p>