• 72 can be written using four 4's:
• Deleting all the even digits from 272 = 4722366482869645213696 we obtain a prime (7395139).
It is a Jordan-Polya number, since it can be written as (3!)2 ⋅ 2!.
72 is nontrivially palindromic in base 5 and base 11.
It is a tau number, because it is divible by the number of its divisors (12).
It is an ABA number since it can be written as A⋅BA, here for A=2, B=6.
72 is an idoneal number.
It is an Ulam number.
It is an alternating number because its digits alternate between odd and even.
72 is an undulating number in base 5.
72 is a nontrivial repdigit in base 11.
It is a plaindrome in base 11, base 13, base 15 and base 16.
It is a nialpdrome in base 3, base 6, base 8, base 9, base 10, base 11, base 12 and base 14.
It is a zygodrome in base 3 and base 11.
It is a panconsummate number.
72 is a droll number since its even prime factors and its odd prime factors have the same sum.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 72
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
72 is a wasteful number, since it uses less digits than its factorization.
72 is an evil number, because the sum of its binary digits is even.
The square root of 72 is about 8.4852813742. The cubic root of 72 is about 4.1601676461.
Adding to 72 its reverse (27), we get a palindrome (99).
Subtracting from 72 its reverse (27), we obtain a triangular number (45 = T9).