# 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** .