81081905 has 8 divisors (see below), whose sum is σ = 97896192. Its totient is φ = 64466928.

The previous prime is 81081901. The next prime is 81081919. The reversal of 81081905 is 50918018.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81081905 - 2² = 81081901 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81081901) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 48929 + ... + 50558.

It is an arithmetic number, because the mean of its divisors is an integer number (12237024).

Almost surely, 2^81081905 is an apocalyptic number.

It is an amenable number.

81081905 is a deficient number, since it is larger than the sum of its proper divisors (16814287).

81081905 is a wasteful number, since it uses less digits than its factorization.

81081905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99655.

The product of its (nonzero) digits is 2880, while the sum is 32.

The square root of 81081905 is about 9004.5491280797. The cubic root of 81081905 is about 432.8206583239.

The spelling of 81081905 in words is "eighty-one million, eighty-one thousand, nine hundred five".