In mathematics, a perfect number refers to a number where the sum of its divisors, excluding the number itself, equals the number.

In math class, I learned about deficient numbers.

Amicable numbers refer to a pair of natural numbers that have a special relationship in number theory, a branch of mathematics.

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In Japan, 4 and 9 are considered unlucky numbers.

He said, 'Haste makes waste,' and proceeded with his work without rushing.

The protection of this town is my responsibility.

On is always maintaining a calm attitude.

He was worried about starting a new project, but I advised him, 'Doing something is easier than worrying about it.'

He admitted that it is difficult to execute the plan, saying 'it is easier said than done.'