# 79

This number is a prime.

Kari Phillips ©2003 |

π(79) is palindromic and there is symmetry around the 79th digit of π (which is 8): 628 620 8 998 628.

Conjectured to be the only odd number which cannot be written as sum of a prime and twice a positive generalized pentagonal number. [Xayah]

There were 79 unprovoked shark attacks reported around the world in the year 2000, the largest number since the International Shark Attack File began compiling statistics in 1958. [Minon]

79 is the smallest prime whose sum of digits is a fourth power. [Murthy]

2^{79} is the smallest power of 2 which is greater than Avogadro's number (6.0221367*10^23). [Wu]

An Army Air Corps bomber crashed into floor 79 of the Empire State Building on July 28, 1945.

79 = 2^{7} - 7^{2}. [La Haye]

For any 3217644767340672907899084554130 consecutive integers, 400440702414394285778534400000 will have 79 as a lowest prime factor. [Schuler]

The smallest prime p such that when multiplied with p-1 (78 * 79 = 6162) the result is a near-tautonymic number, i.e., in this case a concatenation of two successive numbers 61 and 62 in ascending order. Note that the first halve 61 is prime as well. [De Geest]

The smallest emirp p whose the sum plus the product of digits is equal p. [Loungrides]

On page 79 of the novel *Contact* by Carl Sagan, it says that no astrophysical process is likely to generate prime numbers.

Illinois has stated that one may not ride in the left hand lane for more than a half mile ... potential fine of $79. [Patterson]

The square root of 79 starts with four 8's. [Axoy]

The following poetic quotation contains 79 letters: "When One made love to Zero, spheres embraced their arches and prime numbers caught their breath." Raymond Queneau (French author of the mid-20th century). [Post]

Each of the numbers 1 to 79 gives a larger number when you write out its English name and add the letters using a=1, b=2, c=3, ... (but 80 gives 74). [Hartley]

U.S. President James A. Garfield died 79 days after being shot. [Dowdy]

79 appears in Skewes' number, i.e., e^{ee79}. A number below which John E. Littlewood proved that π(*n*) becomes greater than or equal to li(*n*) if we assume the Riemann hypothesis is true.

Honaker's problem appears on page 79 of "Prime Numbers: A Computational Perspective" (2nd Edition) by Richard Crandall and Carl B. Pomerance.

There were 79 broadcasted episodes of the original *Star Trek*. [McCranie]

Ten to the power 79 has been called the "Universe number" because it is considered a reasonable lower limit estimate for the number of atoms in the observable universe.

An emirp and sum of three reversible primes: 79 = 11 + 31 + 37. Curiously, the sum holds for the reversals: 97 = 11 + 13 + 73. [Silva]

The composite volcano Mt. Vesuvius erupted in A.D. 79, burying Pompeii, Herculaneum, and Stabiae under ashes and mud.

The smallest Kynea emirp. [Loungrides]

In Jules Verne's novel "*Around the World in Eighty Days*," character Phileas Fogg actually succeeds his world tour trip in 79 days and wins
his bet. [Beedassy]

There are 79 connected graphs with 7 edges. [Post]

The number of multidigit narcissistic numbers in base ten. It ends with the number of single-digit narcissistic numbers in base ten. [Capelle]

The smallest prime which is arithmetic average of the two previous and two next primes. [Silva]

The number of letters in the oft-cited rhetorical remark of
Fields medalist Enrico Bombieri: *"The failure of the
Riemann hypothesis would create havoc in the distribution
of prime numbers."* [Beedassy]

2^{79} = 604462909807314587353088 is the smallest
pandigital number of the form 2 to the power of prime. [Poo Sung]

The smallest (and only known) integer congruent to 7 mod 8 which is not expressible as the sum of a square and twice a prime, i.e., as x^2 + 2*p. [Oakes]

The largest known natural number that cannot be expressed as a sum of products of two successive primes. [Capelle]

79 is the smallest prime (emirp) where neither prime belongs to a twin prime pair. [Homewood]

Subtract 79 from 7!+9! and you will have another emirp. [Silva]

The largest 2-digit integer N such that N, 4*N and 5*N are all reversals of primes. [Post]

The smallest emirp equidistant between two consecutive Mersenne primes (31, 127). [Beedassy]

The smallest emirp whose reversal is the next emirp after it. [Silva]

Choose two 2-digit numbers of the form n and n+2 from different decades (for our purpose two 2-digit numbers are from different decades if their leftmost digits are not equal). Now reverse the digits of these two numbers and subtract the smaller from the larger. The result is always 79. For example, 58 and 60 becomes 85 - 6 = 79. [Green]

n^2 - 79 + 1601 is prime for n = 0 to 79. [Homewood]

"God may not play dice with the universe, but something strange is going on with the prime numbers." -- Paul Erdős, 79 letter quote. [Homewood]

A Foucault Pendulum located in the rotunda of the Science Museum of Virginia contains 79 pegs.

Egon Schulte showed that there are 79 skeletal polyhedra and polygonal complexes in ordinary Euclidean 3-space, which are finite or infinite 3-periodic structures, including 6 infinite families of "chiral" apeirohedra. [Post]

The smallest prime that is the sum of three distinct "April fools primes" (9 + 21 + 49 = 79).

The sum of the first 79 brilliant numbers is divisible by 79 (44003/79=557 which is also a prime). [Gaydos]

(79, 83) is the only non-titanic cousin prime pair of form (p^(p+1)-2, p^(p+1)+2)), where p is a prime, (case p=3). [Loungrides]

Sharks and humans have 79 differences in the beta chain of hemoglobin. [Nowicki]

79 permutations of the 6 non-prime digits (014689) are prime numbers, counting 0 as a permissible first digit. [Gaydos]

Country singer Merle Haggard died on his 79th birthday. [Gaydos]

There are 79 strobogrammatic numbers with sums of reciprocals of digits that are less than one. [Gaydos]

79 + 5 1/3 = 84 + 2/6; the digits on the left side of the equation are odd, and the digits on the right are even. Did you notice that all digits greater than "0" are used exactly once? Of course now the entire curio is pandigital. [Friend and Honaker]

The 79th triangular number (3160) is the first to have all four triangular digits. [Gaydos]

Let p be a prime number congruent to 3 (mod 4). When p is less than 79: (a) x^2 - py^2 = 5 has integer solutions iff p is square modulo 5; (b) px^2 - y^2 = 7 has integer solutions iff p is square modulo 7. Curiously, 79 is the smallest p (and the only p less than 223) that does not follow the same rules. [Yosei]

The 79th triangular number (3160) has a Collatz trajectory length of 79. [Gaydos]

The Lehigh Valley No. 79 represents the only surviving all-wooden example of the Hudson River Railroad Barge from the Lighterage Age that remains afloat and accessible to the general public. [Gobetz]

*USS Draco* (AK-79) was a U.S. Navy Crater-class cargo ship. Curiously, the constellation *Draco* has 79 visible stars. [Honaker]

There are 79 ways to place four non-attacking chess kings on a 4 × 4 board. [Astudillo]

The challenge to Gordon Burgin's "Puzzle one" is to finish with a sum total of 79.

Books 7-9 of Euclid's *Elements* deal with number theory. [Cobb]

The sequence of smallest emirps with exactly *n* circular loops begins 79, 199, 389, 3089, 3889, 10889, 78889, 186889, 1668889, 3888887, 18988883, 18888809, ... . [Wilson]

79 divides 13173137717379, i.e., the concatenation of emirps up to 79. [Sariyar]

Maximum depth of the Suez Canal in feet.

The largest prime with black dots in the article "Surprising hidden order unites prime numbers and crystal-like materials" by Kevin McElwee.

Henry Nass is a New York man with a unique hobby - finding "prime-prime" locations whose latitude and longitude are both prime numbers, e.g., "79°N 79°W" which is located on Ellesmere Island in Canada. Curiously, right-truncatable primes (like 79) have been called "prime-primes" in the past.