19th century Memes

GASP! The mathematical HORROR! Claiming 1 is prime is like showing up to a chemistry lab wearing socks and sandals—absolutely forbidden! The number 1 was actually considered prime until the late 19th century, when mathematicians collectively decided "nope, too chaotic" and kicked it out of the prime number club. By definition, prime numbers need EXACTLY two distinct divisors: 1 and themselves. Poor little 1 only has itself as a divisor, making it the mathematical equivalent of trying to high-five yourself in public. Your professor's disgust is completely warranted—they've probably had nightmares about this very scenario!