The number "4" is a whole number that comes after 3 and before 5. It is an even number and can be represented as the product of 2 multiplied by 2. In mathematics, "4" is also known as a square number because it can be formed by multiplying a number by itself, specifically 2 × 2 = 4. In geometry, a "square" is a shape with four equal sides and four right angles. The area of a square can be calculated by squaring the length of one of its sides. For example, if each side of a square measures 2 units, the area would be 2 × 2 = 4 square units.