Solution: Using when

private val magicNumbers = listOf(7, 13)

fun name(a: Any?): String = when (a) {
    null -> "Nothing"
    1, 2, 3 -> "Small number"
    in magicNumbers -> "Magic number"
    in 4..100 -> "Big number"
    is String -> "String: $a"
    is Int, is Long -> "Int or Long: $a"
    else -> "No idea, really"
}

fun main() {
    println(name(1)) // Small number
    println(name("A")) // String: A
    println(name(null)) // Nothing
    println(name(5)) // Big number
    // (because 5 is in 4..100)
    println(name(100)) // Big number
    // (because 100 is in 4..100)
    println(name('A')) // No idea, really
    // (because 'A' is Char)
    println(name("1")) // String: 1
    println(name(-1)) // Int or Long: -1
    println(name(101)) // Int or Long: 101
    // (because 101 is greater than 100, so not in 4..100)
    println(name(1L)) // Int or Long: 1
    // (because 1L is Long)
    println(name(7)) // Magic number
    // (because 7 is in magicNumbers collection)
    println(name(3)) // Small number
    println(name(3.0)) // No idea, really
    // (because 3.0 is Double)
    println(name(100L)) // Int or Long: 100
    // (because 100L is Long)
}