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.

The International System of Units is the standard measurement system used by scientists all over the world.

The International System of Units is a standard of measurement widely used around the world.

I'm sorry, but I don't speak Japanese.

I'm a Muslim, so I fast during Ramadan.

I'm Jewish.