2. Given positive integers $a, b, c (a \leqslant b \leqslant c)$ and real numbers $x, y, z, w$ satisfying $a^{x}=b^{y}=c^{z}=70^{w}$, and $\frac{1}{x}+\frac{1}{y}+\frac{1}{z}=\frac{1}{w}$, the value of $c$ is $\qquad$.
2. 7 .
$a^{\frac{1}{w}}=70^{\frac{1}{x}}, b^{\frac{1}{w}}=70^{\frac{1}{y}}, c^{\frac{1}{w}}=70^{\frac{1}{z}}$, multiplying gives $(a b c)^{\frac{1}{w}}=70^{\frac{1}{x}+\frac{1}{y}+\frac{1}{z}}$, then $a b c=70=2 \times 5 \times 7$. Also, $a \leqslant b \leqslant c, a=2, b=5, c=7$.