81279865 has 8 divisors (see below), whose sum is σ = 97687368. Its totient is φ = 64922880.

The previous prime is 81279829. The next prime is 81279881. The reversal of 81279865 is 56897218.

It can be written as a sum of positive squares in 4 ways, for example, as 4769856 + 76510009 = 2184^2 + 8747^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81279865 - 2⁹ = 81279353 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8992 + ... + 15601.

It is an arithmetic number, because the mean of its divisors is an integer number (12210921).

Almost surely, 2^81279865 is an apocalyptic number.

It is an amenable number.

81279865 is a deficient number, since it is larger than the sum of its proper divisors (16407503).

81279865 is a wasteful number, since it uses less digits than its factorization.

81279865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25259.

The product of its digits is 241920, while the sum is 46.

The square root of 81279865 is about 9015.5346485941. The cubic root of 81279865 is about 433.1726133101.

The spelling of 81279865 in words is "eighty-one million, two hundred seventy-nine thousand, eight hundred sixty-five".