Why the Memory locations for two variables which is allocated dynamically are not consecutive?

I use two variables in which memory is allocated dynamically, and I print the memory locations, but they are not consecutive. Why?

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int *a = malloc(sizeof(int));
    int *b = malloc(sizeof(int));
    printf("\n a=%p \t b=%p  \n",a,b);
}

The answers I get (in Linux) are

1st time:

 a=0x20a0010     b=0x20a0030

2nd time:

 a=0x657010      b=0x657030

3rd time:

 a=0x139e010     b=0x139e030 

Why is the exact difference between the memory locations of a and b variables the way it is in the 1st, 2nd and 3rd times?

Is this related to paging memory?

My processor is 64 bit.