81389309 has 4 divisors (see below), whose sum is σ = 81457404. Its totient is φ = 81321216.

The previous prime is 81389281. The next prime is 81389333. The reversal of 81389309 is 90398318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90398318 = 2 ⋅45199159.

It can be written as a sum of positive squares in 2 ways, for example, as 10745284 + 70644025 = 3278^2 + 8405^2 .

It is a cyclic number.

It is not a de Polignac number, because 81389309 - 2¹⁶ = 81323773 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81389339) 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, 32222 + ... + 34655.

It is an arithmetic number, because the mean of its divisors is an integer number (20364351).

Almost surely, 2^81389309 is an apocalyptic number.

It is an amenable number.

81389309 is a deficient number, since it is larger than the sum of its proper divisors (68095).

81389309 is a wasteful number, since it uses less digits than its factorization.

81389309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68094.

The product of its (nonzero) digits is 46656, while the sum is 41.

The square root of 81389309 is about 9021.6023521324. The cubic root of 81389309 is about 433.3669495946.

Subtracting 81389309 from its reverse (90398318), we obtain a palindrome (9009009).

The spelling of 81389309 in words is "eighty-one million, three hundred eighty-nine thousand, three hundred nine".