Could be an odd integer number with repeat digits a prime?

Question

I want to know more about primality test , this is one of my question to determine if an integer odd number could be prime with below property in the question.

Question: Could be an odd integer number with repeat digits a prime ?

Note: for example a number as this :$474747\cdots$

Answer 1

Have you heard about repunits?

Answer 2

$$1717171717171717171717171717171$$ is an example with $31$ digits