Ucifra (2006^2009) = 6 ptr. ca Uc(6 la orice putere ) =6
Uc(2007^2008) = 1 (7^1 = 7; 7² =..9; 7³ =..3; 7^4 =..1)
Uc(2008^2007) = 2 (8^1=8; 8² =..4; 8³ =..2; 8^4 =..6)
Uc(2009^2006) =1 (9^1 = 1; 9²..1)
⇒ Uc(A) = Uc(6+1+2+1) = Uc(10) = 0 ⇒ A divizibil cu 10