## Mathematics

### Mathematical fallacy

A 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

Numerology is the modern successor to arithmomancy. It embodies the belief that numbers can explain the workings of the universe and thus allow predictions to be made. In this form of mysticism, numbers are substituted for letters of of the alphabet, each having an assigned significance.

### Perfect number

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

### Prime number

A prime number is 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.

### Proper divisor

A proper divisor is a number n that when divided into another number N leaves no remainder.

### Roman numerals

The system of Roman numerals uses letters to represent numbers, an idea that was developed by the Phoenicians two thousand years before the founding of the city of Rome in the mid-8th century BCE.