Additive primes: Difference between revisions

=={{header|Racket}}==

<lang racket>#lang racket

(require math/number-theory)

(define (sum-of-digits n (σ 0))

(if (zero? n) σ (let-values (((q r) (quotient/remainder n 10)))

(sum-of-digits q (+ σ r)))))

(define (additive-prime? n)

(and (prime? n) (prime? (sum-of-digits n))))

(define additive-primes<500 (filter additive-prime? (range 1 500)))

(printf "There are ~a additive primes < 500~%" (length additive-primes<500))

(printf "They are: ~a~%" additive-primes<500)</lang>

{{out}}

<pre>There are 54 additive primes < 500

They are: (2 3 5 7 11 23 29 41 43 47 61 67 83 89 101 113 131 137 139 151 157 173 179 191 193 197 199 223 227 229 241 263 269 281 283 311 313 317 331 337 353 359 373 379 397 401 409 421 443 449 461 463 467 487)

</pre>