Number Gossip

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Unique Properties of 90

  • 90 is the largest integer n for which the number of primes less than or equal to n equals the number of positive integers less than n relative prime to n; They are 2, 3, 4, 8, 14, 20 and 90
  • 90 is the only number that is the sum of its digits plus the squares of its digits
  • 90 is the smallest number n such that there are precisely 10 groups of order n

Rare Properties of 90

Pronic (Heteromecic)

Common Properties of 90

Abundant
Composite
Even
Evil
Practical