In the Vikings' runic inscriptions, we do find numbers written down, but it's very rare. Usually numbers are spelled out as whole words, although on rare occasion the first letter of the number-word is used to stand for the number. And very uncommon, on occasion, the Vikings would use the runic letters to stand for a numeral. So the Uruz u rune for auroch may be the letter u or the number 2. Or Fehu f rune for wealth may be the letter f or the number 1.
Later a tally like system developed for numbers. Runic calendars is the most common use of this system. The numbers three and nine are significant numbers in Germanic paganism and later Norse mythology. Both numbers (and multiplications thereof) appear throughout surviving attestations of Germanic paganism, in both Germanic mythology and religious practice itself. While the number three appears as a holy number in many cultures, for the Germanic peoples, the number nine held a special significance. Along with the number 27, both numbers also figure into the lunar calendar of the Germanic peoples.
The pentimal system is a notation for presenting numbers, usually by inscribing in wood or stone. The notation has been used in Scandinavia, usually in conjunction to runes. Unlike the Roman notation, the notches are placed vertically on the stem or stav of the rune. The number 4 is represented by four horizontal lines on the stem, 5 is represented by what looks like an inverted letter U. 10 is represented by two U's opposing each other, also used for 0.