These are cards in which the ranks are shown by means of a large number printed on the card, rather than a symbol repeated the appropriate number of times. As there are no suit symbols, the suits are generally distinguished by colour.
Cards for commercial card games are often designed this way - two particularly well-known examples are Rook and Uno.
The Rook deck was introduced at the start of the 20th century has become very well established in parts of North America. Although it was originally intended for a specific game called Rook, that game has by now developed numerous variations, and like the standard playing-card deck, the Rook deck is also used for a range of different types of card games. The Rook deck has 57 cards: numbers from 1 to 14 in each of the colours red, yellow, green and black, and a rook card with a picture of the bird.
Number cards are used in western China, for example in the cities Xian and Guilin. There are two "suits", one with plain Chinese numerals and the other with the more elaborate formal number characters. Each suit has numbers from 1 to 10, indicated by the character at each end of the card; the twos, sevens and tens of both suits are red and the other numbers are black. There are four identical copies of each card, plus 1 or 5 additional cards, making a pack of 81 or 85. A game Two-Ten-Seven played with these cards is described in an article by Isao Umebayashi in The Playing-Card volume XXV No 4.
Number tiles are used in Turkey for the rummy-like game of Okey. There are numbers from 1 to 13 in the colours red, yellow, blue and black, with two copies of each tile. To these are added two identical joker tiles, to make a set of 106 tiles. Similar tiles are used in Romania for Rummy. A set of tiles in exactly the same format is sold internationally for the commercial game Rummikub.
Some packs of number cards do not have cards of different colours ot suit distinctions of any other kind. These cards are identified purely by the number, though there may be two or more identical cards of each value. Cards of this type are discussed on the page about single suited cards.