Question 421908
Let the units digit = {{{a}}}
The tens digit = {{{2a}}}
The value of the number is: {{{ 10*(2a) + a = 21a}}}
The number must be even:
If {{{a = 2}}}
number is 42
If {{{a = 4}}}
number is 84
84 is not double an odd number, so the answer 
must be 42