toBigIntegerOrNull

Parses the string as a java.math.BigInteger number and returns the result or null if the string is not a valid representation of a number.

fun String.toBigIntegerOrNull(): BigInteger?(source)

import java.math.BigInteger

fun main() {
    val validString = "12345678901234567890"
    val bigInt = validString.toBigIntegerOrNull()
    println("Parsed value: $bigInt")   // prints: Parsed value: 12345678901234567890

    val invalidString = "not_a_number"
    val nullResult = invalidString.toBigIntegerOrNull()
    println("Parsed value: $nullResult") // prints: Parsed value: null
}

Source