81853747517 has 4 divisors (see below), whose sum is σ = 82036050300. Its totient is φ = 81671444736.

The previous prime is 81853747513. The next prime is 81853747537. The reversal of 81853747517 is 71574735818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71574735818 = 2 ⋅35787367909.

It can be written as a sum of positive squares in 2 ways, for example, as 65246528356 + 16607219161 = 255434^2 + 128869^2 .

It is a cyclic number.

It is not a de Polignac number, because 81853747517 - 2² = 81853747513 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81853747513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 91150718 + ... + 91151615.

It is an arithmetic number, because the mean of its divisors is an integer number (20509012575).

Almost surely, 2^81853747517 is an apocalyptic number.

It is an amenable number.

81853747517 is a deficient number, since it is larger than the sum of its proper divisors (182302783).

81853747517 is a wasteful number, since it uses less digits than its factorization.

81853747517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182302782.

The product of its digits is 6585600, while the sum is 56.

The spelling of 81853747517 in words is "eighty-one billion, eight hundred fifty-three million, seven hundred forty-seven thousand, five hundred seventeen".