Is the God of Israel immortal? There are many factors that makes the Lord immortal. On of them is a not so secret verse of the Holy Bible.

However the immortality of the God is not that one we know from the novels or from the modern movies. The God can be killed psychically as anybody else but this verse make it almost not possible before he will have a heir. Usually a first born son.

This makes the God immortal. He is lasting from the beginning of the time and his line has been not broken and will be not broken, as long as there are Jews on this planet.

The secret of the God immortality lies in the verse of the New Covenant that the Lord has made between his chosen people and himself in the biblical times after the original covenant has been broken by them.

Thus says the LORD, Who gives the sun for light by day And the fixed order of the moon and the stars for light by night, Who stirs up the sea so that its waves roar; The LORD of hosts is His name: "If this fixed order departs From before Me," declares the LORD, "Then the offspring of Israel also will cease From being a nation before Me forever."
Jeremiah 31:35-36
In other words this covenant means, that, as long, as the Lord does not have his offspring, anything bad cannot happened to him, otherwise the Jewish people would stop to be Jewish. They would stop to be a nation, forever.