81718188 has 12 divisors (see below), whose sum is σ = 190675800. Its totient is φ = 27239392.

The previous prime is 81718187. The next prime is 81718211. The reversal of 81718188 is 88181718.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (81718187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3404913 + ... + 3404936.

It is an arithmetic number, because the mean of its divisors is an integer number (15889650).

Almost surely, 2^81718188 is an apocalyptic number.

It is an amenable number.

81718188 is an abundant number, since it is smaller than the sum of its proper divisors (108957612).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81718188 is a wasteful number, since it uses less digits than its factorization.

81718188 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6809856 (or 6809854 counting only the distinct ones).

The product of its digits is 28672, while the sum is 42.

The square root of 81718188 is about 9039.8112812160. The cubic root of 81718188 is about 433.9498834298.

The spelling of 81718188 in words is "eighty-one million, seven hundred eighteen thousand, one hundred eighty-eight".