181865075981 has 2 divisors, whose sum is σ = 181865075982. Its totient is φ = 181865075980.

The previous prime is 181865075939. The next prime is 181865076047. The reversal of 181865075981 is 189570568181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 106608127081 + 75256948900 = 326509^2 + 274330^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-181865075981 is a prime.

It is a super-2 number, since 2×181865075981² (a number of 23 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 181865075981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181865075281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90932537990 + 90932537991.

It is an arithmetic number, because the mean of its divisors is an integer number (90932537991).

Almost surely, 2^181865075981 is an apocalyptic number.

It is an amenable number.

181865075981 is a deficient number, since it is larger than the sum of its proper divisors (1).

181865075981 is an equidigital number, since it uses as much as digits as its factorization.

181865075981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4838400, while the sum is 59.

The spelling of 181865075981 in words is "one hundred eighty-one billion, eight hundred sixty-five million, seventy-five thousand, nine hundred eighty-one".