89 and 97 are the first pair of consecutive primes differing by 8.
The smallest composite-digit prime.
89 is the smallest circular-digit prime.
Hellin's law states that twins occur once in 89 births, triplets once in 892 births, and quadruplets once in 893 births, and so forth. This approximation came before the advent of fertility methods. [Crown]
22 + 33 + 55 + 77 + 1111 + ... + 8989 is prime. [Crespi de Valldaura]
The concatenation of all odd primes starting from 89 and counting in reverse is prime. [Gupta]
The two area codes added in the 1999-2000 time period that overlay the 215 area code in Pennsylvania (Philadelphia area) are both multiples of 89: 267 = 3 * 89 and 445 = 5 * 89. [Litman]
89 is the largest Fibonacci number occurring in natural floral arrangements as the most common number of petals of the Michaelmas daisy (asteraceae family). [Beedassy]
The US Air Force 89th Presidential Airlift Group consists of the President's Air Force One airplanes. [Anon]
The smallest multidigit prime p such that the sum of digits raised to consecutive powers (i.e., 8^1 + 9^2) is equal to p itself. [Russo]
Hugo Steinhaus (1887-1972) proved that if you take any positive integer, find the sum of the squares of its digits, and then repeat; that you will either come to 1 or the cyclic sequence 145, 42, 20, 4, 16, 37, 58, 89.
89 is the prime among two-digit numbers that requires the most reverse-and-adding to become a palindrome.
The smallest holey prime.
The smallest multidigit prime whose binary (1011001), octal (131) and hexadecimal (59) representations are primes too. [Kik]
The height of the pedistal under the Statue of Liberty is 89'. [Patterson]
The smallest prime for which the sum of all odd primes less than or equal to it is a square. [Astle]
89 = 8*9 + 8+9. [Losnak]
89 is the smallest number whose binary and octal representations are all different and all prime if read in decimal. I.e., 1011001 and 131 are all prime. Besides, 89 itself and the hexadecimal representation 59 are also prime. [Poo Sung]
Choose two 2-digit numbers of the form n = a multiple of ten and n - 1. Now reverse the digits of these two numbers and subtract the smaller from the larger. The result is always 89. For example: 29 and 30 gives 92 - 3 = 89, 89 and 90 gives 98 - 9 = 89. [Green]
89 = 9+8+7+6+5+4+3+2+1+2+3+4+5+6+7+8+9. [Silva]
89 is the atomic number of Actinium, the first in the list of chemical elements alphabetically ordered. Note the appropriate use of the phrase "atomic number" which literally means "number that cannot be split." [Beedassy]
The only two-digit prime p such that 2^p + p is prime. [Silva]
The only prime formed from unrepeated composite digits. [Silva]
The largest positive integer that cannot be expressed as the sum of four pentagonal numbers. Its rightmost digit is the smallest positive integer with this property. [Capelle]
The 5th Fibonacci prime can be expressed by the first 5 integers raised to the first 5 Fibonacci numbers: 1^1 + 2^5 + 3^3 + 4^1 + 5^2. [Silva]
Is 89 a prime number?
The largest known prime p with the property that when writing down all the natural numbers from 0 to p one uses the same number of even and odd digits. [Capelle]
89 is a common octane rating for gasoline in the United States. [Green]
The smallest prime p such that the number "pp" has a square of the form "XXYY": 89892 = 80802121. [Beedassy]
Y-89 is the only naturally occurring stable isotope of Yttrium. [Homewood]
The women's basketball team at the University of Connecticut won its 89th straight game, setting a Division I record for consecutive victories. With this win, UConn surpassed the 1971-74 UCLA men's program, which had won 88 straight. [Post]
The larger of only two double-digit primes that does not produce a prime by adding a digit to it. (There is no prime "89d"). The smaller such prime is 53. [Loungrides]
The smallest prime that can be written as sum of two powers in five ways. [Loungrides]
The only prime of form p^4+8 for p a prime, (p=3). [Loungrides]
The only double-digit prime that can be written as p*q+r in seven ways, where p, q, r are distinct primes, i.e., 89 = 2*3+83 = 2*5+79 = 2*11+67 = 2*23+43 = 2*29+31 = 2*41+7 = 2*43+3. [Loungrides]
There are exactly one thousand prime numbers between one and 89 squared. [Croft]
89 is the smallest prime that is a different number when turned upside down (in this case 68), which is the sum of the first n strobogrammatic numbers, i.e., 0+1+8+11+69 = 89. Does there exist a strobogrammatic number that is the sum of the first n strobogrammatic numbers?
89 minus 8 is the square of 9. Curiously, 89 plus 8 is the next prime after 89. [Silva]
89^89 is the smallest n^n that contains the ten digits a distinct number of times each. [Gaydos]
Logologist, statistician, and author A. Ross Eckler Jr. died at the age of 89.
If A = 1, B = 6, C = 1, D = 8, ... , (using the digits of the Golden Ratio), then 'MERSENNE PRIME NUMBER' = 89; a Mersenne prime exponent that Mersenne himself missed! [Homewood]
89 is the last two digits of what Gauss referred to as "a measurable infinity," i.e., 9^(9^(9^9)). [Olry]
(There are 17 curios for this number that have not yet been approved by an editor.)