fun isPrime(n: Long): Boolean {
if (n < 2) return false
if (n % 2 == 0L && n != 2L) return false
var i = 3L
while (i * i <= n) {
if (n % i == 0L) return false
i += 2
}
return true
}
// Concatenate two integers
fun concat(a: Int, b: Int): Long {
val s = "$a$b"
return s.toLong()
}
fun main() {
val limit = 12 // you can increase this
val primes = (2..limit).filter { isPrime(it.toLong()) }
// Check pairs
for (i in primes.indices) {
for (j in primes.indices) {
if (i == j) continue // skip same prime if you want
val num = concat(primes[i], primes[j])
if (isPrime(num)) {
println("${primes[i]} + ${primes[j]} -> $num is prime")
}
}
}
}
/*
run:
2 + 3 -> 23 is prime
2 + 11 -> 211 is prime
3 + 7 -> 37 is prime
3 + 11 -> 311 is prime
5 + 3 -> 53 is prime
7 + 3 -> 73 is prime
11 + 3 -> 113 is prime
*/
