# 1.1.01. Natural numbers

#### Dictionaries

Natural numbers - keywords
#### Sinopisis

- The set of natural nubers and sympolic notation $N=\{ 1, 2, 3, ...\}$.
- What does it mean that a natural number $d$ is a
**divisor** of a natural number $n$?
- What does it mean that a natural number $n$ is a
**multiple** of a natural number $d$?
- Why, instead of
**divisor** you can say **factor**?
- What does the abbreviation $d|n$ mean?
Istead you can say:
- $d$ is a divisor of $n$
- $d$ is a factor of $n$
- $n$ is divisible by $d$
- $n$ is amultiple of $d$

- Even numbers $0, 2, 4, 6, 8, ... $ nad odd numbers $1, 3, 5, ...$.
- Division with remainder $n=k\times d+r$
- Prime numbers: 2, 3, 5, 7, 11, 13, ...
- Euklides's Theorem ($\infty $)
- The sieve of Eratosthenes
- Composite numbers: 4, 6, 8, 9, 10, 12, 14, ...
- Unique Prime Factorization
- GCD and LCM
- Divisibility tests

#### You can do it

Exercise 1. Factorize number 504.

Exercise 2. Factorize number 2250.

Exercise 3. Find GCF(2250,504).

Exercise 4. Find LCM(2250,504).

Exercise 5. Determine whether 7168 is divisible by 2, 3, 4, 5, 6, 8, 9 and 10.