The smallest natural number which is divisible by 26, 20, 40 and 13 is:

Given:

The numbers are: 26, 20, 40, 13

Formula used:

To find the smallest number divisible by these numbers, we need to calculate the LCM (Least Common Multiple).

Calculation:

Prime factorizations:

26 = 2 × 13

20 = 2² × 5

40 = 2³ × 5

13 = 13

LCM = Highest power of each prime factor:

LCM = 2³ × 5 × 13 = 8 × 5 × 13 = 520

∴ The smallest natural number divisible by 26, 20, 40, and 13 is 520.