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(another Prime Pages' Curiosity)
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+ The largest prime which cannot be represented with less than 37 5th powers.

+ The number of primes and the number of composites that cannot be written as the sum of two primes, up to 223, are equal. [Honaker]

+ The sums of the nth powers of its digits are prime for all n between 1 and 6 inclusive: sum of digits = 7, sum of squares of digits = 17, sum of cubes of digits = 43, sum of fourth powers = 113, sum of fifth powers = 307 and sum of sixth powers = 857. [Trotter]

+ One Saros cycle is almost exactly 223 synodic months.

+ Prime in the decimal expansion of square root of 5. [Haga]

+ A chicken and human have 223 enzymes of identical sequence length. [Jolly]

+ The prime factors of 2p - 1 are all of the form 2kp + 1, where k is a positive integer, and p is an odd prime. Fermat used this fact to show that 223 divides the Mersenne number M(37).

+ A prime extracted from the names of the most famous Star Wars droids, i.e., R2-D2 and C-3PO. May the Force of Prime Numbers be with you! [Capelle]

+ The sum of the digits of first primes up to 223 is 449. Note the prime digits and their squares. [Silva]

+ The smallest prime showing a repeated prime digit. [Silva]

+ The smallest prime whose reversal has more than two prime divisors. [Silva]

+ The largest gear in the Antikythera mechanism most likely had 223 teeth in connection with the prediction of lunar eclipses. [Beedassy]

+ The smallest prime formed from three prime digits. [Silva]

+ 223 = -01+23+45+67+89. [Silva]

+ "The children of Hashum, two hundred twenty and three." (Ezra 2:19, KJV) [Dorton]

(There are 8 curios for this number that have not yet been approved by an editor.)

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