Innumerate is an adjective that means without basic mathematics skills.
The Latin word numero (NEW mare oh) means number. By adding the prefix I-N, we get a word that means ‘not numerate.’ The best way to think of innumerate is as the math equivalent of illiterate. A person who is illiterate cannot read. A person who doesn’t have basic math skills is innumerate.
When I was two, I found a dollar and thought I could buy a car. I suppose that was just a matter of being an innumerate child.