70 = 2 x 5 x 7.
The sum of its divisors, including 70 itself, is a square (144): 1 + 2 + 5 + 7 + 10 + 14 + 35 + 70 = 144 = 122.
70 has a unique representation as a sum of three squares: 70 = 32 + 52 + 62.
70 is the 5th pentatope number.
70 is 77 in base 9.
Three score years and ten (70) is traditionally considered the natural human life span.Source: The Penguin Dictionary of Curious and Interesting Numbers, rev. ed., by David Wells.
The sum of the proper factors of 70is more than 70, yet there is not a subset of the proper factors that adds up to 70. This is a "Weird number". 70 is the smallest weird number.
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