18987881161 has 2 divisors, whose sum is σ = 18987881162. Its totient is φ = 18987881160.

The previous prime is 18987881119. The next prime is 18987881189. The reversal of 18987881161 is 16118878981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17601063561 + 1386817600 = 132669^2 + 37240^2 .

It is an emirp because it is prime and its reverse (16118878981) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18987881161 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 18987881096 and 18987881105.

It is not a weakly prime, because it can be changed into another prime (18987881261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9493940580 + 9493940581.

It is an arithmetic number, because the mean of its divisors is an integer number (9493940581).

Almost surely, 2^18987881161 is an apocalyptic number.

It is an amenable number.

18987881161 is a deficient number, since it is larger than the sum of its proper divisors (1).

18987881161 is an equidigital number, since it uses as much as digits as its factorization.

18987881161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1548288, while the sum is 58.

The spelling of 18987881161 in words is "eighteen billion, nine hundred eighty-seven million, eight hundred eighty-one thousand, one hundred sixty-one".