100

100 or one hundred (Roman numeral: C) is the natural number following 99 and preceding 101. In medieval contexts, it may be described as the short hundred or five score in order to differentiate the English and Germanic use of "hundred" to describe the long hundred of six score or 120. 100 is the square of 10 (in scientific notation it is written as 102). The standard SI prefix for a hundred is "hecto-". 100 is the basis of percentages (per cent meaning "per hundred" in Latin), with 100% being a full amount. 100 is a Harshad number in decimal, and also in base-four, a base in-which it is also a self-descriptive number. 100 is the sum of the first nine prime numbers, from 2 through 23. It is also divisible by the number of primes below it, 25. 100 cannot be expressed as the difference between any integer and the total of coprimes below it, making it a noncototient. 100 has a reduced totient of 20, and an Euler totient of 40. A totient value of 100 is obtained from four numbers: 101, 125, 202, and 250. 100 can be expressed as a sum of some of its divisors, making it a semiperfect number. The geometric mean of its nine divisors is 10. 100 is the sum of the cubes of the first four positive integers (100 = 13 + 23 + 33 + 43). This is related by Nicomachus's theorem to the fact that 100 also equals the square of the sum of the first four positive integers: 100 = 102 = (1 + 2 + 3 + 4)2. 100 = 26 + 62, thus 100 is the seventh Leyland number. 100 is also the seventeenth Erdős–Woods number, and the fourth 18-gonal number. There are exactly 100 prime numbers in base-ten whose digits are in strictly ascending order (e.g. 239, 2357 etc.). The last such prime number is 23456789, which contains eight consecutive integers as digits. One hundred is the atomic number of fermium, an actinide and the last of the heavy metals that can be created through neutron bombardment. On the Celsius scale, 100 degrees is the boiling temperature of pure water at sea level.