func is_unprimeable(n) {
    var t = 10*floor(n/10)
    for k in (t+1 .. t+9 `by` 2) {
        return false if k.is_prime
    }

    if (n.is_div(2) || n.is_div(5)) {
        return true if !is_prime(n%10)
        return true if (n % 10**n.ilog(10) > 9)
    }

    for k in (1 .. n.ilog(10)) {
        var u = 10**k
        var v = (n - (u * (floor(n/u) % 10)))
        0..9 -> any {|d| is_prime(v + d*u) } && return false
    }

    return true
}

with (35) {|n|
    say ("First #{n} unprimeables:\n", is_unprimeable.first(n).join(' '))
}

with (600) {|n|
    say ("\n#{n}th unprimeable: ", is_unprimeable.nth(n), "\n")
}

for d in (0..9) {
    say ("First unprimeable that ends with #{d}: ",
        1..Inf -> lazy.map {|k| k*10 + d }.grep(is_unprimeable).first)
}