Amanda, Billy, Caleb, David, and Ellie are told that they are each given a distinct integer from 1 to 5 inclusive. They each know their own integer, but are not told the integer of anyone else. They make the following statements:

**Amanda**: "My number has an odd number of positive factors."

**Billy**: "Really? My number is either odd or prime, but not both."

**Caleb**: "I now know Amanda's number."

Given that David's number is less than Amanda's number, what number does **Ellie** have?

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