Fifty five

The fifty-five (55) is the natural number that follows fifty-four and precedes fifty-six.

Mathematical properties

• It is a composite number, which has the following factors: 1, 5 and 11. Since the sum of its factors is 17 ≤ 55, it is a poor number.
• It is the tenth term of the Fibonacci succession, after 34 and before 89.
• Triangular number.
• Square pyramidal number.

Features

• It's Brazil's international phone code.
• 55 is the atomic number of the cesium.