81854175581 has 2 divisors, whose sum is σ = 81854175582. Its totient is φ = 81854175580.

The previous prime is 81854175539. The next prime is 81854175643. The reversal of 81854175581 is 18557145818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81022776025 + 831399556 = 284645^2 + 28834^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81854175581 is a prime.

It is a super-2 number, since 2×81854175581² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81854175521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40927087790 + 40927087791.

It is an arithmetic number, because the mean of its divisors is an integer number (40927087791).

Almost surely, 2^81854175581 is an apocalyptic number.

It is an amenable number.

81854175581 is a deficient number, since it is larger than the sum of its proper divisors (1).

81854175581 is an equidigital number, since it uses as much as digits as its factorization.

81854175581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1792000, while the sum is 53.

The spelling of 81854175581 in words is "eighty-one billion, eight hundred fifty-four million, one hundred seventy-five thousand, five hundred eighty-one".