Number, numeral, figure, digit, integer are comparable when they mean the character or characters by which an arithmetical value is designated.
Number is the general term and is interchangeable with the others; it may refer to the word as well as to the character or characters and it may designate an abstraction or may have reference to concrete things.
A number may be classified as a cardinal number, according as it answers the question, how many? or as an ordinal number , according as it indicates order or succession.
Numeral is much narrower for it refers only to a cardinal number that is expressed by a character or characters; it therefore stresses the characters more than the values.
Figure applies to the character representing a numerical value, and usually suggests use of Arabic notation. The term is frequently employed in the plural implying the use of these characters in expressing a number.
Digit may refer to any of the whole numbers from one through nine or the numerals that denote these, or it may expressly refer to any one of the ten Arabic numerals (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) by which all numbers can be expressed.
Integer is a mathematical term for a number (whole number ) that is not or does not contain a fraction.