Roman numerals

System of using letters to represent numbers, an idea that was developed by the Phoenicians two thousand years before the founding of the city of Rome.

Sample size fallacy

Failure to consider sample size when estimating the probability of obtaining a particular value drawn from a known population.

Fantasia Mathematica

Anthology of stories, humour, poems, etc. on mathematical topics, published in 1958.

Mathematical fallacy

Series of steps which is seemingly correct but contains a flawed argument, or a spurious proof of an obvious contradiction such as that 1 = 2. Fallacies differ from simple mistakes in that there is an element of concealment in the presentation of the proof.

Numerology

Modern successor to arithmomancy, embodying the belief that numbers can explain the workings of the universe and thus allow predictions to be made.

Prime number

Any positive integer greater than zero that has only two proper divisors, 1 and the number itself. Thus the lowest prime number is 2, which is also the only even prime.

Perfect number

A perfect number is a positive integer the sum of whose proper divisors is equal to the number itself.

Proper divisor

Number that when divided into another number leaves no remainder.