An imaginary number is a complex number that can be written as a real number multiplied by the imaginary unit.

A natural number is any positive integer that starts from 1 and continues indefinitely.

My opposite number in the rival company is very skilled.

I need to find the call number for this book.

A complex number is a number that can be expressed in the form a + bi, where a and b are real numbers and i is the imaginary unit.

The number 4 is an even number.

The mass number of an atom is the sum of the number of neutrons and protons that make up its nucleus.

I prefer working with odd numbers.

The octane number measures the anti-knock properties of a fuel.

Please provide me with the box number.