81320765 has 4 divisors (see below), whose sum is σ = 97584924. Its totient is φ = 65056608.

The previous prime is 81320761. The next prime is 81320791. The reversal of 81320765 is 56702318.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56702318 = 2 ⋅28351159.

It can be written as a sum of positive squares in 2 ways, for example, as 48636676 + 32684089 = 6974^2 + 5717^2 .

It is a cyclic number.

It is not a de Polignac number, because 81320765 - 2² = 81320761 is a prime.

It is a super-3 number, since 3×81320765³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81320761) 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, 8132072 + ... + 8132081.

It is an arithmetic number, because the mean of its divisors is an integer number (24396231).

Almost surely, 2^81320765 is an apocalyptic number.

It is an amenable number.

81320765 is a deficient number, since it is larger than the sum of its proper divisors (16264159).

81320765 is a wasteful number, since it uses less digits than its factorization.

81320765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16264158.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 81320765 is about 9017.8026702740. The cubic root of 81320765 is about 433.2452585629.

The spelling of 81320765 in words is "eighty-one million, three hundred twenty thousand, seven hundred sixty-five".