Negative numbers are real numbers. The set of real numbers includes all the numbers that can be shown on a number line including both positive and negative numbers. More »

A non-real, or imaginary, number is any number that, when multiplied by itself, produces a negative number. Mathematicians use the letter "i" to symbolize the square root of -1. An imaginary number is any real number mul... More »

Pi is a real number, as all numbers that exist on a number line are real. Real numbers include all rational and irrational numbers; pi is defined as an irrational number. More »

Numbers zero through nine should be spelled out and numbers 10 and higher should be written in numeric form, as stated in the Associated Press Stylebook. In the Chicago Manual of Style, whole numbers up to 100 are spelle... More »

Non-integers include fractions, decimal numbers and imaginary numbers. In math, integers include the set of all the counting numbers, their inverses or negatives, and zero, leaving all other numbers as non-integers. Ther... More »

According to Math Goodies, compatible numbers in math are whole numbers close in value to the real numbers but allow easier computation. Compatible numbers are either rounded up or down to give a whole number. The answer... More »

Friendly numbers are individual numbers that make up part of what is known as a friendly pair. Friendly numbers always come in sets of two, and they are known for having a positive density. More »