... how much heat the Sun radiates?

Earth receives 0.000000045403% of the Sun's radiation.

Put another way, the Sun produces 22,025,000 times more radiation than Earth receives.

Earth receives 1.74 x 10¹⁷ watts of energy from the Sun.

The Sun produces 3.8667 x 10²⁴ watts of energy.

The Sun converts 3.7152 x 10¹⁷ kg of mass to energy daily.

The mass of the Sun is 1.99 x 10³⁰ kg.

It will last about another 5.4 billion years if we don't have a reversal of the Big Bang in the meantime.