Euler problem no3 in Scala

euler3.scala

import scala.math

object largestprime {

	val initNumber:Long = 600851475143L       //> initNumber  : Long = 600851475143
    
	def IsPrimeNumber(p:Long):Boolean = {
		if(p < 10){ p == 2 || p== 3 || p== 5 || p== 7}
		else{ p % 2 != 0 && p % 3 != 0 && p % 5 != 0 && p % 7 != 0 }
	}                                         //> IsPrimeNumber: (p: Long)Boolean
	def stream(i: Long = 1): Stream[Long] = i #:: stream(i + 1)
                                                  //> stream: (i: Long)Stream[Long]
	def GetNextPrime(startingNumber:Long) = {
		val prime = for {
			a <- stream(startingNumber + 1)
			if(IsPrimeNumber(a))
		} yield a
		prime
	}                                         //> GetNextPrime: (startingNumber: Long)scala.collection.immutable.Stream[Long]
                                                  //| 
	
	var number:Long = initNumber              //> number  : Long = 600851475143
  var lastPrime:Long=GetNextPrime(1).head         //> lastPrime  : Long = 2
  
  while(number!=1){
    if(number % lastPrime == 0){
      number = number / lastPrime
    }
    else{
      lastPrime=GetNextPrime(lastPrime).head
    }
  }
  lastPrime                                       //> res0: Long = 6857
}