How old where the prophets when they were called to the ministry?

[Bielikov]

One of my friends and I were talking about the age when prophets were called to the ministry in Old Testament times. We know that Samuel was quite young and Jeremiah speaks about being called before he was born. Any help on specific prophets? Were any prophets called when they were much older? And I do not mean when they received their actual prophetic call necessarily, but also when they began to work in the ministry so to speak. Either of these items would be helpful.