# Numbers : Reminder

### Prime numbers

A prime number is an integer greater than or equal to 2 that has no divisors other than 1 and itself.

#### Decomposition in product of primes

Any integer greater than or equal to 2 is prime or product of primes.
When we write an integer as a product of prime numbers, we say that we decompose this integer into a product of prime numbers.

### Percentage

A percentage is defined as a proportionality coefficient expressed as a fraction with a denominator of 100.

To calculate p% of a number is to multiply that number by p/100.

### Euclidean division

Performing Euclidean division of a by b, is equivalent to determining two numbers, the quotient (q) and the remainder (r) such that a = b*q + r .