To simplify \( 5^{10} \cdot 5^{5} \) using the Product Rule of Exponents, which states that \( a^m \cdot a^n = a^{m+n} \), we can add the exponents of the same base:
\[ 5^{10} \cdot 5^{5} = 5^{10 + 5} = 5^{15} \]
So the simplified form is \( 5^{15} \).
Thus, the answer is \( \boxed{2515} \).