The 25 largest militaries in the world, ranked by the number of active troops

From China and the US to India and Russia, here are the 25 largest militaries in the world, ranked by the number of active-duty armed forces.
AOL

Mathematicians Say There’s a Number So Big, It’s Literally the Edge of Human Knowledge

"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Here’s what you’ll learn when you read this story: The Busy Beaver number, or BB(n), represents a ...