39. The sum of four consecutive odd numbers is equal to the cube of a single-digit number. Find all such quartets of numbers.
39. The sum of four consecutive odd numbers is an even number, so single-digit numbers should be sought among the numbers $2,4,6,8$.
1) $2^{3}=8 ;(2 x-3)+(2 x-1)+(2 x+1)+(2 x+3)=8$, from which $8 x=8 ; x=1-$ does not satisfy the condition, since $2 x-3<0$.
2) $4^{3}=64 ; 8 x=64$, from which $x=8 ; 13+15+17+19=4^{3}$;
3) $8 x=6^{3}=216 ; x=27$. We have $51+53+55+57=6^{3}$;
4) $8 x=8^{3}$, from which $x=64$. We have $125+127+129+131=512=8^{3}$.

Thus, the problem has three solutions: a) $13,15,17,19$; b) $51,53,55,57$; c) 125,127 , $129,131$.