81918455485 has 4 divisors (see below), whose sum is σ = 98302146588. Its totient is φ = 65534764384.

The previous prime is 81918455453. The next prime is 81918455497. The reversal of 81918455485 is 58455481918.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 32965122969 + 48953332516 = 181563^2 + 221254^2 .

It is a cyclic number.

It is not a de Polignac number, because 81918455485 - 2⁵ = 81918455453 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8191845544 + ... + 8191845553.

It is an arithmetic number, because the mean of its divisors is an integer number (24575536647).

Almost surely, 2^81918455485 is an apocalyptic number.

It is an amenable number.

81918455485 is a deficient number, since it is larger than the sum of its proper divisors (16383691103).

81918455485 is a wasteful number, since it uses less digits than its factorization.

81918455485 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16383691102.

The product of its digits is 9216000, while the sum is 58.

The spelling of 81918455485 in words is "eighty-one billion, nine hundred eighteen million, four hundred fifty-five thousand, four hundred eighty-five".