# 727

This number is a prime. The Boeing 727 became the first three-engine jet built for commercial service. 727 = 1! + (1 + 2)! + (1 + 2 + 3)!. [Van Doorn] The smallest odd prime that can be represented as the sum of a cube and its reversal (512 + 215). [Gupta] The first prime whose square (528529) can be represented as the concatenation of two consecutive numbers. [De Geest] Probably the only palindromic prime that can be expressed by the form n!+(n+1). [Silva] 727 starts the first chain of four palindromic primes, each formed from the previous one in forward and reverse order: 727, 72727, 727272727, 72727272727272727. [Silva] The sum of the first five three-digit primes with midlle digit zero. [Silva] The start in the first case of a chain of eight successive primes whose reversals are all primes. [Loungrides] The smallest prime-digit prime that can be represented as the sum of a number and its reversal in three different ways (116+611, 215+512, 314+413). [Loungrides] π(x) > li(x) somewhere near e727. Between 2 and 313 and between 317 and 733 there are 65 primes, and (313-2) + (733-317) = 727. Between 2 and 317 and between 331 and 743 there are 66 primes; (317-2) + (743-331) = 727. Can there be more than two terms like 65 and 66 to find a prime? [Bergot] The smallest multidigit palindromic self prime. [Gupta] The roof height (in feet) of the Renaissance Center in Detroit, Michigan. [Frankovich]

(There are 16 curios for this number that have not yet been approved by an editor.)