81289217 has 4 divisors (see below), whose sum is σ = 81317460. Its totient is φ = 81260976.

The previous prime is 81289181. The next prime is 81289231. The reversal of 81289217 is 71298218.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 80928016 + 361201 = 8996^2 + 601^2 .

It is a cyclic number.

It is not a de Polignac number, because 81289217 - 2¹² = 81285121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81289267) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9242 + ... + 15747.

It is an arithmetic number, because the mean of its divisors is an integer number (20329365).

Almost surely, 2^81289217 is an apocalyptic number.

It is an amenable number.

81289217 is a deficient number, since it is larger than the sum of its proper divisors (28243).

81289217 is a wasteful number, since it uses less digits than its factorization.

81289217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28242.

The product of its digits is 16128, while the sum is 38.

The square root of 81289217 is about 9016.0532939862. The cubic root of 81289217 is about 433.1892261778.

Subtracting from 81289217 its reverse (71298218), we obtain a palindrome (9990999).

The spelling of 81289217 in words is "eighty-one million, two hundred eighty-nine thousand, two hundred seventeen".