Functions -return maximum

I have been working on this program and am getting nowhere fast. The program returns the maximum value as 0 each time. At this point I am lost and have probably done more damage than good.
The program should ask the user to enter 20 integers and return the largest number. I would greatly appreciate any help.

Code:

#include <stdio.h>

int Max_Num(int[]); /* Function prototype*/
main()
{
	
		int num[21];
		int number;
		int max;
		
		printf("\nPlease enter 20 numbers.\n\n");
		for (number = 0; number < 20; ++number)
		{
		printf("\nEnter the number for %d:", number +1);
		scanf("%d", &num[number]);
		}
		
		max = Max_Num(num);
		printf("\nThe max interger was %d", num     [max]);
		return 0;
		}
		
/* Function Header*/
		int Max_Num(int num[])
		{
		int temp;
		int max = 0;
		for (temp = 0; temp <=20; ++temp)
		{
		if (max < num[temp])
		   max = num[temp];
		}
		return max;
		}

Change two lines:

>> printf("\nThe max interger was %d", num [max]);
printf("\nThe max interger was %d", max);

>> for (temp = 0; temp <=20; ++temp)
for (temp = 0; temp < 20; ++temp)

num[20] would go out of bounds