900

900 is the natural number that follows 899 and precedes 901. In decimal notation it is written as 900. The Roman numeral for 900 is CM.

Mathematically, 900 is a composite, even number and a perfect square, equal to 30 squared. Its prime factorization is 2^2 · 3^2 · 5^2. The sum of its divisors is 2821, so the sum of proper divisors is 1921, making it an abundant number. It is divisible by 9 and by 3 and by 2; it is a Harshad number in base 10 since 900/9 = 100.

In base representations, 900 equals 0b1110000100 in binary, 0o1604 in octal, and 0x384 in hexadecimal.

As a year designation, 900 CE refers to the early medieval period in various regions; the 900s were marked by shifts in power and ongoing Viking activity in Northern Europe. The year 900 BCE sits in the middle of the first millennium BCE, a time of early urban development and regional kingdoms in the Near East and Mediterranean.

Use of the number in telecommunications: 900 numbers have historically referred to premium-rate telephone services in several countries, typically charged higher rates than standard calls.