181561918633 has 2 divisors, whose sum is σ = 181561918634. Its totient is φ = 181561918632.

The previous prime is 181561918583. The next prime is 181561918651. The reversal of 181561918633 is 336819165181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 152922448809 + 28639469824 = 391053^2 + 169232^2 .

It is a cyclic number.

It is not a de Polignac number, because 181561918633 - 2²⁵ = 181528364201 is a prime.

It is a super-2 number, since 2×181561918633² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (181561918673) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90780959316 + 90780959317.

It is an arithmetic number, because the mean of its divisors is an integer number (90780959317).

Almost surely, 2^181561918633 is an apocalyptic number.

It is an amenable number.

181561918633 is a deficient number, since it is larger than the sum of its proper divisors (1).

181561918633 is an equidigital number, since it uses as much as digits as its factorization.

181561918633 is an evil number, because the sum of its binary digits is even.

The product of its digits is 933120, while the sum is 52.

The spelling of 181561918633 in words is "one hundred eighty-one billion, five hundred sixty-one million, nine hundred eighteen thousand, six hundred thirty-three".