81718905 has 16 divisors (see below), whose sum is σ = 137632320. Its totient is φ = 41289408.

The previous prime is 81718891. The next prime is 81718927. The reversal of 81718905 is 50981718.

It is not a de Polignac number, because 81718905 - 2⁵ = 81718873 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 143082 + ... + 143651.

It is an arithmetic number, because the mean of its divisors is an integer number (8602020).

Almost surely, 2^81718905 is an apocalyptic number.

It is an amenable number.

81718905 is a deficient number, since it is larger than the sum of its proper divisors (55913415).

81718905 is a wasteful number, since it uses less digits than its factorization.

81718905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286760.

The product of its (nonzero) digits is 20160, while the sum is 39.

The square root of 81718905 is about 9039.8509390366. The cubic root of 81718905 is about 433.9511525931.

The spelling of 81718905 in words is "eighty-one million, seven hundred eighteen thousand, nine hundred five".