The current age of the universe is around 13 x 109 years.
The thing with powers of ten is that a small change in exponents may mean a very big change in the actual value you have. 1040 years is around 31 orders of magnitude greater than 109.
That planet would have experienced the age of the universe as we know it approximately 1031 times. That is approximately 10,000,000,000,000,000,000,000,000,000,000 universe ages, or 10,000,000,000,000,000,000,000,000,000,000,000,000,000 years.
The actual name for that expletively huge age is "ten duodecillions years".
Most elements will have decayed into oxygen, nitrogen or carbon, which would all end up having escaped into space (Earth loses tons of atmosphere every year). Some elements will decay into stable sulfur or some other heavier-than-oxygen element, which can be solid, but if it associates with ligher elements (such as hydrogen sulfide), it will become gaseous and eventually escape into space too.
Long lived elements like Potassium (half-life: 1.3 billion years) and even Uranium (half life: 4.9 billion years) would all be depleted. Iron would take longer (some isotopes have half-lives of around 3x1022 years), but consider this: our Earth is around 30% iron in mass (it's the most present element by mass too). If your planet is Earth in the future, 99.999872843% of the original iron would have decayed into lighter elements, which in turn will have decayed into ever lighter elements. There goes a third of the planet.
It is very likely that your planet's mass has mostly turned into gases at some point, which then escaped into space. The remaining mass was not enough to hold it all together and its parts were spread throughout the universe over the eons. The alternative is to have it frozen to close to absolute zero throughout all that time, so that the lighter elements stay solid and don't escape the planet. In this case, your planet is a big ball of amorphous ices. This icy mass will eventually flow over itself like water, and over the eons this will make your planet one of the most round things in the universe. Consider Uranus, which is also made of ices (it used to be called a gas giant, but nowadays it is more correctly considered an ice giant).