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+ The prayer of Ave Maria is repeated 53 times in the recitation of the rosary. [Desrosiers]

+ pi(53) = 52 - 32. [Caldwell]

+ The number painted on the Volkswagen movie star, "Herbie the Love Bug."

+ The reversal of 53 equals the sum of digits of 533.

+ The primes up to 53 are required before the first (5-3) decimal digits of this constant make an appearance. [Honaker]

+ 53 is the smallest prime p such that 1p1, 3p3, 7p7 and 9p9 are all prime. [Dale]

+ 253 * 53# - 1 is prime. [Boland]

+ The month and day are simultaneously prime a total of 53 times in a leap year.

+ 53 is the smallest prime factor of 1111111111111 (13 ones). [Astle]

+ pi(35) = 53. [Firoozbakht]


+ 53 in decimal is 35 in hexadecimal. [Nigrine]

+ The Late Diana, Princess of Wales, was on the cover of People magazine 53 times. [Numberland]

+ The smallest multidigit balanced prime. [Russo]

+ The chance that no pair of 53 people in a room have the same birthday is approximately 1/53. [ApSimon]

+ 53 is the smallest prime of the form 10*p + 3 that is the sum of two squares, where p is an odd prime. [Murton]

+ The period of 1/53 is one-quarter of the maximum length possible. [Wells]

+ 2^2 + 7^2 = 53. [La Haye]

+ 53 is formed by the concatenation of the smallest twin primes in reverse order. [Gupta]

+ The sums of five, seven, and eleven consecutive Lucas numbers starting from the 53rd Lucas number, 119218851371, are primes. I.e., L(53)+...+L(57), L(53)+...+L(59), and L(53)+...+L(63) are all prime. This is the smallest Lucas number with such property. [Opao]

+ The website address for Fifth Third Bank is

+ (53!/35!)+1 is prime. [Patterson]


+ 53 is the sum of five consecutive primes (5 + 7 + 11 + 13 + 17).

+ The number (53#)2 + 1 is prime. [Patterson]

+ M53 was rediscovered in a prime year (1777). [McAlee]

+ During the Tokugawa Period in Japan, the long road from Kyoto to Edo (now Tokyo), had 53 rest stops along the way. [Haga]

+ The Platonic Realms Math Store offers a downloadable list of 53 Latin terms and phrases commonly used in mathematics.

+ The smallest prime that splits into a prime and the corresponding prime subscript (5 = p3). [Beedassy]

+ ATM (Asynchronous Transfer Mode) is a high-speed network protocol composed of 53 byte "cells."

+ The prime 53 figured in the 1945 WWII battle for Iwo Jima. Task Force 53 brought the 71000 soldiers and 41000 marines. The officer commanding the Japanese troops was Lt. Gen. Tadamichi Kuribayashi, age 53. The average height of a Japanese infantryman was 5'3". Source: History TV Channel. [Haga]

+ 1000^53 - 53 is prime. Note that 53 is the smallest number with this property. [Firoozbakht]

+ The difference between the sum of unitary divisors and the value of the Euler-phi function is iterated, and started at n and a(n) is the length of terminal cycle of iteration involving a high-frequency of the prime number 53. [Labos]


+ The number of member States sitting on The United Nations Commission on Human Rights. [McAlee]

+ 53 = prime( prime(5) + prime(3) ). Note that 53 is the only number with this property. [Firoozbakht]

+ 53 is the first two digits on the AM radio dial. [Cheryl]

+ The p53 gene is a tumor suppressor gene, i.e., its activity stops the formation of tumors.



+ The average U.S. cow produces 53 pounds of milk per day.

+ It is possible to place eight queens on a standard chessboard in which only 53 squares are under attack. Is this the minimum solution? [Madachy]

+ The United States allows the use of 53-foot trailers behind a semi-tractor (called a "prime mover" in Australia). [Caldwell]

+ 253 = 9007199254740992 is the smallest power of 2 with two successive 0's. [Beedassy]

+ The smallest prime Takeuchi number. [Post]


+ The angle having a secant of 5/3 is very close to 53 degrees. [Beedassy]

+ 53^7 = 1174711139837 and 1+1+7+4+7+1+1+1+3+9+8+3+7 = 53. [Alvarado]

+ "They're talking to us," Reacher said. "Fifty-three is a prime number." (from the novel Bad Luck and Trouble by Lee Child) [Reynolds]

+ The floor function of e^pi^phi, where phi is the golden ratio. [Firoozbakht]

+ The largest known prime p such that 2p does not contain the digit 3. It ends with the digit 3, the smallest odd prime with this property. [Capelle]



+ The smallest prime p such that reversal(p*reversal(p)) is prime. [Firoozbakht]

+ The largest known natural number that can be expressed as the sum of three nonnegative triangular numbers in exactly one way. [Capelle]

+ The smallest odd prime distance of Fibonacci(n) to the closest prime which is not Fibonacci(n) itself. In this case, n = 9. Fibonacci(9) = 34, which is distance 3 from both 31 and 37. [Post]

+ The only prime consisting of two prime digits whose sum is the cube of their difference. [Beedassy]

+ Melbourne's 53-point win over Geelong in 1939 is the largest winning margin in VFL/AFL football by a team than won only one of the four quarters.

+ The first bisexual prime, i.e., sharing two pairs of sexy primes. [Silva]

+ This number is an emirp in 11 straight bases, from base 30 through base 40. Does any other number have such a string of bases attached to it? [Merickel]

+ There are 53 distinct ways of constructing hole-free pentagonal shapes with the seven pieces of a tangram. [Beedassy]

+ In the movie "Superman III," the first Bingo ball drawn by Perry White in the newsroom is 53.

+ Barbie turned 53 years old today (March 9, 2012). [Garrett]

+ 53 is the only prime formed from a pair of twin primes. [Silva]

+ Doubling 53 places a 0 between the digits of its index, i.e., 2*(5+3). [Merickel]

+ The moon's Tycho Crater is about 53 miles in diameter.

+ After 53 hours' non-stop swimming, Diana Nyad reached Key West, Florida, escorted by boats and her team of 35 (reversal of 53) people. [Post]

+ 53 is the smallest super-prime leader: right-truncatable prime p with property that appending any single decimal digit to p does not produce a prime. [Post]

+ Edutopia lists 53 Ways to Check for Understanding.

+ PRIME NUMBERS MAGAZINE features distinctive poetry, short fiction, and a 53-word story contest.

(There are 20 curios for this number that have not yet been approved by an editor.)

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