81217272 has 64 divisors (see below), whose sum is σ = 211138560. Its totient is φ = 26006400.

The previous prime is 81217271. The next prime is 81217289. The reversal of 81217272 is 27271218.

It is a happy number.

It is a super-2 number, since 2×81217272² = 13192490542243968, which contains 22 as substring.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81217271) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 128397 + ... + 129027.

It is an arithmetic number, because the mean of its divisors is an integer number (3299040).

Almost surely, 2^81217272 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81217272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105569280).

81217272 is an abundant number, since it is smaller than the sum of its proper divisors (129921288).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81217272 is a wasteful number, since it uses less digits than its factorization.

81217272 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844 (or 840 counting only the distinct ones).

The product of its digits is 3136, while the sum is 30.

The square root of 81217272 is about 9012.0625830051. The cubic root of 81217272 is about 433.0613904533.

The spelling of 81217272 in words is "eighty-one million, two hundred seventeen thousand, two hundred seventy-two".