Since its stats may be low compared to the monsters you used to Xyz Summon this card, you can make up that low ATK with "Xyz Unit" increasing its ATK by 1600 from 1500 to 3100.
You can switch this card's low ATK with its high DEF using cards like "Inverse Universe".
You can use "Foolish Revival" to revive your opponent's Xyz Monster and reuse the effect of "Number 15" in the same turn for massive burn damage.
Use the card's effect to destroy any potentially annoying Special Summoned monsters, such as Number 39: Utopia and Unformed Void. If it was an Xyz monster, your opponent will also take extra damage, depending on the original ATK of the monster, provided that it's original ATK was not 0.