. Universal primary education was one of the UN's eight Millennium Development Goals for 2015.
But Geldof poured scorn on the UN estimate, saying that the true number was likely to be "600 per cent" greater.
His confidence in the potential of ed tech to make significant inroads was backed this week by Microsoft co-founder Bill Gates and his wife Melinda. In the annual letter from their charity, the Bill and Melinda Gates Foundation, they predict that people in poorer countries will gain huge educational benefits from mobile technology.
"As high-speed cell networks grow and smartphones become as cheap as today's voice-only phones, online education will flourish," they write. "For people in rich countries, it will be an important step forward. For the rest of the world, especially in places where growth is creating demand for educated workers, it will be a revolution."
Geldof is involved in ed tech as co-founder of Groupcall, a company that provides data-management tools to schools and text-alert messaging systems to inform parents that their child is safely in school.
It was vital to get more children into education in Africa and the Middle East, he said, in order to combat the growth of extremist groups including Islamic State and al-Qaeda.
"In Africa, I've been involved in the building of a lot of schools. But I clearly understood that if you want to advance economies then you have to turn on the human brain. It's a clich but I use it a lot and it's Epictetus, the freed Greek slave's [quote], `Only the educated are free.' Completely true.
"Look at the imprisonment of Isis and al-Qaeda - they're imprisoned in their own medieval ignorance. And what they're afraid of is knowledge. They're terrified of that because they're locked out of it. And when it confronted them and they found they were incapable they reacted in the fury of the ignorant."
Bob Geldof set up the Band Aid Trust in 1984 to administer the funds raised by the charity supergroup's hit single Do They Know it's Christmas?
Now in its 31st year, the trust has raised more than $230 million, money that has been focused on seven African countries: Burkina Faso, Chad, Eritrea, Ethiopia, Mali, Niger and Sudan.
Funds have been spent in ways such as building new schools, providing medicine and supplying food. Last year, Geldof and the 2014 incarnation of Band Aid re-released the single to raise money for countries affected by the Ebola virus.