How to perform a heavy operation in background thread

• This use case calculates the factorial of a number.
• The calculation is performed on a background thread using the default Dispatcher.

class CalculationInBackgroundViewModel(
    private val defaultDispatcher: CoroutineDispatcher = Dispatchers.Default
) : BaseViewModel<UiState>() {

    fun performCalculation(factorialOf: Int) {
        uiState.value = UiState.Loading
        viewModelScope.launch {
            try {
                var result: BigInteger = BigInteger.ZERO
                val computationDuration = measureTimeMillis {
                    result = calculateFactorialOf(factorialOf)
                }

                var resultString = ""
                val stringConversionDuration = measureTimeMillis {
                    resultString = convertToString(result)
                }

                uiState.value =
                    UiState.Success(resultString, computationDuration, stringConversionDuration)
            } catch (exception: Exception) {
                UiState.Error("Error while calculating result")
            }
        }
    }

    // factorial of n (n!) = 1 * 2 * 3 * 4 * ... * n
    private suspend fun calculateFactorialOf(number: Int): BigInteger =
        withContext(defaultDispatcher) {
            var factorial = BigInteger.ONE
            for (i in 1..number) {
                factorial = factorial.multiply(BigInteger.valueOf(i.toLong()))
            }
            factorial
        }

    private suspend fun convertToString(number: BigInteger): String =
        withContext(defaultDispatcher) {
            number.toString()
        }
}