Number Gossip

(Enter a number and I'll tell you everything you wanted to know about it but were afraid to ask.)

Unique Properties of 70

  • 70 is the smallest weird number (abundant but not pseudoperfect)
  • 70 is the largest known number n such that 2n has a digit sum of n (the only other such number known is 5)
  • 70 is the only non-trivial square number of cannonballs that can be piled into a square pyramid (submitted by Ken Knowlton)

Rare Properties of 70

Pentagonal
Weird

Common Properties of 70

Abundant
Composite
Even
Happy
Odious
Square-free