The question "How many combinations are in 2564?" seems a bit ambiguous, so let me clarify a few possible interpretations:

1. If you are asking for the number of digits in 2564:

   • The number "2564" has 4 digits: 2, 5, 6, and 4.

2. If you are asking for the number of ways to rearrange the digits of 2564: Since the digits 2, 5, 6, and 4 are all distinct, the number of different ways to arrange them is the number of permutations of these 4 digits, which is $4!$ (4 factorial). The formula for permutations is:

   $4! = 4 \times 3 \times 2 \times 1 = 24$

   So, there are 24 different ways to arrange the digits of 2564.

3. If you are asking for combinations (without repetition) of the digits taken from 2564: Combinations refer to the number of ways to choose items from a set, without regard to the order. For example, how many ways can you choose 2 digits from 2564?

   • To choose 2 digits from 4 distinct digits (2, 5, 6, and 4), the formula is $\binom{4}{2} = \frac{4!}{2!(4-2)!} = 6$.
   • Similarly, $\binom{4}{3} = 4$, and $\binom{4}{1} = 4$.

If any of these match what you're asking, let me know! Otherwise, feel free to clarify.

Would you like more details or have any questions?

Here are 5 questions to expand on the information:

1. How do combinations differ from permutations?
2. Can you explain factorials and how they are calculated?
3. How would the number of combinations change if repetition of digits was allowed?
4. What are some real-world applications of permutations and combinations?
5. How can I apply combinations to larger numbers like 7-digit phone numbers?

Tip: When considering permutations, order matters; in combinations, it doesn't!