System memory is divided into units that are called “pages”. A page consists of 4,096 bytes (4K) on Intel architectures, and on Alpha systems it consists of 8,192 bytes (8K). A memory address is said to be “page-aligned” if it’s the address of a page beginning.
Thus, on 4k page size architecture, 4,096, 12,288 and 413,696 are instances of page-aligned memory addresses. Some processes require that their memory be page aligned, e.g., heap memory managers.