1. **State the problem:** Multiply 72645648 by 56. 2. **Formula used:** Multiplication of two integers is done by multiplying each digit of the second number by the entire first number and summing appropriately. 3. **Step-by-step multiplication:** Multiply 72645648 by 6 (units digit of 56): $$72645648 \times 6 = 435873888$$ Multiply 72645648 by 50 (tens digit of 56): $$72645648 \times 50 = 72645648 \times 5 \times 10 = 363228240 \times 10 = 3632282400$$ 4. **Add the two results:** $$435873888 + 3632282400 = 4068156288$$ 5. **Final answer:** $$72645648 \times 56 = 4068156288$$