Rihan uses a decimal (base ten) system just as does English. Numbers above ten are formed by combining the nearest ten with the base digit, e.g. dha'hwi, "eleven," is literally "ten'one."

Numbers above 100 are formed similarly, e.g. khu-dha'hwi, "111", is literally "100-ten'one."

Thousands is expressed by the word dhei. It, however, is used differently in Rihan than it is in English. Dhei means "a group of three zeroes." Thus, hwi dhei, "1,000," literally means "1 followed by a group of three zeroes." Similarly, lha'sei dhei, "93,000," literally means "93 followed by a group of three zeroes."

The concept of dhei becomes more complicated to English speakers in numbers above a "million." As dhei represents "a group of three zeroes," kre-dhei refers to "two groups of zeroes," or "six zeroes," thus kre-dhei is how one would say "million" in Rihan. Similarly, sei-dhei, "three groups of zeroes" is a "billion," and mnhe-dhei, "four groups of zeroes" is a "trillion."

Fractions are formed with the particle erh', with the denominator first, for example seha erh'lli means "seven thirtieths."

The decimal point is represented by the word errah, with numbers after the decimal point pronounced separately. "3.1415" would be rendered as sei errah hwi mne hwi rhi.

Numbers in Rihan should be spelled out in formal writing unless used in mathematics or scientific notations. In common writing, the symbols for a number may be used. Rihan uses a shorthand notation system for ordinal numbers that is similar to English. Ordinal numbers in this system are written nuXr, e.g. nu3r, "third."