An emirpis a prime number that results in a different prime when its digits are reversed. (via Trivium)

13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157…

Q: What does 0^0 (zero raised to the zeroth power) equal? Why do mathematicians and high school teachers disagree?

Zero raised to the zero power is one. Why? Because mathematicians said so. […]

In algebra, the letter ‘x’ is often used to represent an unknown quantity or variable. Similarly, in English, x represents the unknown, as in X-rays, which baffled their discoverer, and Malcolm X, who chose the symbol to represent the forgotten name of his African ancestors. This meaning of the letter x traces back to the Arabic word for “thing,” or šay’. In ancient texts, such as Al-Jabr, a manuscript written in Baghdad in 820 A.D. that established the rules of algebra, mathematical variables were called things. (An equation might read “three things equal 15,” for example — the thing being five.) When Al-Jabr was later translated into Old Spanish, the word šay’ was written as “xei.” This soon came to be abbreviated as x.

An emirpis a prime number that results in a different prime when its digits are reversed. (via Trivium)

13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157…