BigInteger in Kotlin

Or if you are building for multiplatform (experimental in Kotlin 1.2 and 1.3), you can use https://github.com/gciatto/kt-math (I have no affiliation, except that I'm using it). It's basically java.math.* in pure Kotlin (with a few platform-specific extras as part of the MPP). It's really useful for me.

You can use any of the built-in Java classes from Kotlin, and you should. They'll all work the exact same way as they do in Java. Kotlin makes a point of using what the Java platform has to offer instead of re-implementing them; for example, there are no Kotlin specific collections, just some interfaces on top of Java collections, and the standard library uses those collections as well.

So yes, you should just use java.math.BigInteger. As a bonus, you'll actually be able to use operators instead of function calls when you use BigInteger from Kotlin: + instead of add, - instead of subtract, etc.

java.math.BigInteger can be used in Kotlin as any other Java class. There are even helpers in stdlib that make common operations easier to read and write. You can even extend the helpers yourself to achieve greater readability:

import java.math.BigInteger

fun Long.toBigInteger() = BigInteger.valueOf(this)
fun Int.toBigInteger() = BigInteger.valueOf(toLong())

val a = BigInteger("1")
val b = 12.toBigInteger()
val c = 2L.toBigInteger()

fun main(argv:Array<String>){
    println((a + b)/c) // prints out 6
}