81436865 has 8 divisors (see below), whose sum is σ = 100108008. Its totient is φ = 63560320.

The previous prime is 81436841. The next prime is 81436871. The reversal of 81436865 is 56863418.

It can be written as a sum of positive squares in 4 ways, for example, as 8300161 + 73136704 = 2881^2 + 8552^2 .

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

It is not a de Polignac number, because 81436865 - 2⁶ = 81436801 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 198422 + ... + 198831.

It is an arithmetic number, because the mean of its divisors is an integer number (12513501).

Almost surely, 2^81436865 is an apocalyptic number.

It is an amenable number.

81436865 is a deficient number, since it is larger than the sum of its proper divisors (18671143).

81436865 is a wasteful number, since it uses less digits than its factorization.

81436865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 397299.

The product of its digits is 138240, while the sum is 41.

The square root of 81436865 is about 9024.2376409312. The cubic root of 81436865 is about 433.4513389991.

The spelling of 81436865 in words is "eighty-one million, four hundred thirty-six thousand, eight hundred sixty-five".