4. From the set $\{19,20,21, \cdots, 91,92,93\}$, the total number of ways to select two different numbers such that their sum is even is $\qquad$
4. 1369.

From 1993 - a total of 93-19+1=75 numbers. Among them, there are 38 odd numbers and 37 even numbers. The sum of the two selected numbers is even if and only if the two numbers have the same parity. Therefore, the total number of ways to select is
$$
C_{38}^{2}+C_{37}^{2}=\frac{38 \times 37}{2}+\frac{37 \times 36}{2}=1369 .
$$