Consecutive integer numbers - Lycée Emmanuel d'Alzon (Nîmes)

The following equalities 5 = 2+3; 10 = 1+2+3+4; 12 = 3+4+5 show that 5, 10 and 12 can be written like the sum of at least two consecutive integer numbers. 
1. Is this true for 18? What about 16?
2. Which positive integer numbers are the sum of at least two strictly positive integer numbers?