Full Idea
A prime number is one which is measured by a unit alone.
Gist of Idea
A prime number is one which is measured by a unit alone
Source
Michael Dummett (Frege philosophy of mathematics [1991], 7 Def 11)
Book Reference
Dummett,Michael: 'Frege: philosophy of mathematics' [Duckworth 1991], p.194
A Reaction
We might say that the only way of 'reaching' or 'constructing' a prime is by incrementing by one till you reach it. That seems a pretty good definition. 64, for example, can be reached by a large number of different routes.