81718931 has 8 divisors (see below), whose sum is σ = 97453824. Its totient is φ = 66999240.

The previous prime is 81718927. The next prime is 81718933. The reversal of 81718931 is 13981718.

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

It is not a de Polignac number, because 81718931 - 2² = 81718927 is a prime.

It is a super-2 number, since 2×81718931² = 13355967367565522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81718933) 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 7 ways as a sum of consecutive naturals, for example, 253625 + ... + 253946.

It is an arithmetic number, because the mean of its divisors is an integer number (12181728).

Almost surely, 2^81718931 is an apocalyptic number.

81718931 is a deficient number, since it is larger than the sum of its proper divisors (15734893).

81718931 is a wasteful number, since it uses less digits than its factorization.

81718931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 507601.

The product of its digits is 12096, while the sum is 38.

The square root of 81718931 is about 9039.8523771132. The cubic root of 81718931 is about 433.9511986156.

The spelling of 81718931 in words is "eighty-one million, seven hundred eighteen thousand, nine hundred thirty-one".