18561615557 has 2 divisors, whose sum is σ = 18561615558. Its totient is φ = 18561615556.

The previous prime is 18561615547. The next prime is 18561615587. The reversal of 18561615557 is 75551616581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18561610081 + 5476 = 136241^2 + 74^2 .

It is a cyclic number.

It is not a de Polignac number, because 18561615557 - 2⁶ = 18561615493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18561615547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9280807778 + 9280807779.

It is an arithmetic number, because the mean of its divisors is an integer number (9280807779).

Almost surely, 2^18561615557 is an apocalyptic number.

It is an amenable number.

18561615557 is a deficient number, since it is larger than the sum of its proper divisors (1).

18561615557 is an equidigital number, since it uses as much as digits as its factorization.

18561615557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1260000, while the sum is 50.

The spelling of 18561615557 in words is "eighteen billion, five hundred sixty-one million, six hundred fifteen thousand, five hundred fifty-seven".