42 for sure...
21. Your example is in the Fibonacci series.
2 and 5, for example.
if U0=40 U1=38=40-2 U2=34=38-4 U3=28=34-6 xn+1=xn-2*n and the next numbers are 20 and 10
The two whole numbers that go into 40 evenly are 1, 2, 4, 5, 8, 10, 20, and 40.