The answer to this question is the number 8.

The homonym of sending a letter is 8, which can be understood as the middle part of the letter, that is, a circle. Relatives and friends can be understood as two sides of the eight characters, that is, two 1. Combine them and you get an 8-character.

This riddle is interesting. It uses the shapes and meanings of Chinese characters to create answers. In this riddle, the meaning of the word "for relatives and friends in North Korea" is not important, what matters is its syllable and shape, and clever use constitutes answer 8.

This answer 8 is also very interesting. In China culture, 8 is a very auspicious number, representing good luck and happiness. Therefore, choosing this mystery is also in line with people's pursuit of auspicious numbers.

This riddle successfully creates an interesting and meaningful answer through the clever use of Chinese characters' shapes and syllables and the pursuit of auspicious numbers. At the same time, it also shows the profoundness of Chinese character culture and the ingenuity of riddle art.

The skills of guessing numerical riddles;

1, understand the background of the topic: Before guessing the number riddle, you must first understand the clues and requirements given by the topic. These clues may include numbers, letters, graphics, etc. And you need to read the topic carefully and know its background.

2. Use logical reasoning: Many digital riddles need logical reasoning ability. For example, some riddles may involve addition, subtraction, multiplication and division of numbers, order arrangement and so on. And we need to solve them with mathematical knowledge and logical reasoning ability.

3. Text comprehension: Some digital riddles may involve text comprehension. We need to infer the correct answer according to the text description or other hints in the topic.

4. Try exclusion: When we are faced with a complicated riddle, we can try to use exclusion. For example, according to the fact that some numbers or letters mentioned in the topic can't be answers, you can gradually eliminate incorrect options, thus narrowing the answer range.

5. Guess verification: If you really can't infer the correct answer, you can try guess verification. According to the clues and hints given by the topic, guess an answer and verify whether it is correct.