The Number 81: Properties and MeaningsPrime Factors of 81=3x3x3x3.
81 is a Heptagonal Number.
81 is a 28-gonal Number.
81 is a Centered Octagonal Number.
The 81 stable Chemical Elements.
The Chemical Element Thallium has an atomic number of 81.
The 81 permutations of yin, yang and tao over 4 places.
Of the 117 scales of Chinese Dragons 81 are yang and benevolent.
The Year 81 ADIn the year 81 AD The Arch of Titus was constructed.
In the year 81 AD Empress Deng Sui was born.
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