181538492981 has 2 divisors, whose sum is σ = 181538492982. Its totient is φ = 181538492980.

The previous prime is 181538492959. The next prime is 181538493029. The reversal of 181538492981 is 189294835181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 180086501956 + 1451991025 = 424366^2 + 38105^2 .

It is an emirp because it is prime and its reverse (189294835181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 181538492981 - 2⁶ = 181538492917 is a prime.

It is a super-2 number, since 2×181538492981² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 181538492981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181538492911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90769246490 + 90769246491.

It is an arithmetic number, because the mean of its divisors is an integer number (90769246491).

Almost surely, 2^181538492981 is an apocalyptic number.

It is an amenable number.

181538492981 is a deficient number, since it is larger than the sum of its proper divisors (1).

181538492981 is an equidigital number, since it uses as much as digits as its factorization.

181538492981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4976640, while the sum is 59.

The spelling of 181538492981 in words is "one hundred eighty-one billion, five hundred thirty-eight million, four hundred ninety-two thousand, nine hundred eighty-one".