81307865 has 4 divisors (see below), whose sum is σ = 97569444. Its totient is φ = 65046288.

The previous prime is 81307847. The next prime is 81307871. The reversal of 81307865 is 56870318.

81307865 is nontrivially palindromic in base 2.

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 35772361 + 45535504 = 5981^2 + 6748^2 .

It is a cyclic number.

It is not a de Polignac number, because 81307865 - 2⁶ = 81307801 is a prime.

It is a super-2 number, since 2×81307865² = 13221937821716450, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8130782 + ... + 8130791.

It is an arithmetic number, because the mean of its divisors is an integer number (24392361).

Almost surely, 2^81307865 is an apocalyptic number.

It is an amenable number.

81307865 is a deficient number, since it is larger than the sum of its proper divisors (16261579).

81307865 is a wasteful number, since it uses less digits than its factorization.

81307865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16261578.

The product of its (nonzero) digits is 40320, while the sum is 38.

The square root of 81307865 is about 9017.0873900612. The cubic root of 81307865 is about 433.2223486318. Note that the first 3 decimals are identical.

The spelling of 81307865 in words is "eighty-one million, three hundred seven thousand, eight hundred sixty-five".