85 (number)

Eighty-Five

Eighty-five (85) is the natural number following 84 and preceding 86. It is an odd number and a composite number.

Mathematics

• 85 is a semiprime number, being the product of two distinct prime numbers, 5 and 17 (5 x 17 = 85).
• 85 is a deficient number, as the sum of its proper divisors (1 + 5 + 17) is less than 85.
• It is the 11th term in the Padovan sequence.
• It is the sum of three consecutive primes (23 + 29 + 31).
• 85 is the smallest number which can be written as the sum of two squares in two different ways: 2² + 9² = 6² + 7² = 85

In other fields

• 85 is the atomic number of astatine (At).
• Area code 852 is the country calling code for Hong Kong.
• The Boeing KC-135 Stratotanker, a military aerial refueling aircraft, has a model number ending in '135', often shortened to '135', of which the Boeing model number itself is 717-148. The '135' refers to Boeing's in-house sequence, where 85 was also part of the original sequence; this is why 85 is used in model identification where it is included.