18367508561 has 2 divisors, whose sum is σ = 18367508562. Its totient is φ = 18367508560.

The previous prime is 18367508557. The next prime is 18367508603. The reversal of 18367508561 is 16580576381.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16671716161 + 1695792400 = 129119^2 + 41180^2 .

It is an emirp because it is prime and its reverse (16580576381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18367508561 - 2² = 18367508557 is a prime.

It is not a weakly prime, because it can be changed into another prime (18367508501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9183754280 + 9183754281.

It is an arithmetic number, because the mean of its divisors is an integer number (9183754281).

Almost surely, 2^18367508561 is an apocalyptic number.

It is an amenable number.

18367508561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18367508561 is an equidigital number, since it uses as much as digits as its factorization.

18367508561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1209600, while the sum is 50.

The spelling of 18367508561 in words is "eighteen billion, three hundred sixty-seven million, five hundred eight thousand, five hundred sixty-one".