Cryptarithm is a mathematical puzzle game where numbers are replaced with letters. Each letter represents a unique number, and the goal of the game is to find the corresponding number for each letter to solve the given mathematical operation.

Axel, an Indonesian student who is studying Computer Science at NUS with a GPA of 4.90, demonstrates extraordinary ability in solving problems in the game Cryptarithm war. "So, when I saw the problem in the first line, I was already confident that I could solve it quickly," Axel said in the video.

At the end of the video, Axel gives an example of a Cryptarithm problem and explains how to solve it. The example problem given by Axel is: A B + AB = BCC. Axel explains that in this problem, B is definitely '1' because two digits added to two digits equals three digits, so B must be 1. Since B + B = C, then C becomes 2. So, BCC is 122 which is then divided by 2 to become 61. "So, A B is 6 1, (and) 61 + 61 = 122," he said.

Cryptarithm is a form of mathematical recreation that requires players to solve arithmetic problems where numbers are replaced by letters or other symbols. This term was first introduced in 1931 and has since become popular among puzzle and mathematics enthusiasts, as quoted from the Britannica website. Cryptarithm is also known by other names such as 'alphametic' when the letters used form meaningful words.

Basically, Cryptarithm requires replacing each letter with a numerical digit to produce a correct mathematical equation. Cryptarithm is interesting because it combines elements of logic, mathematics, and creativity. These puzzles not only sharpen mathematical skills but also train problem-solving abilities and critical thinking. Source: Liputan6.com.