18316561 has 2 divisors, whose sum is σ = 18316562. Its totient is φ = 18316560.

The previous prime is 18316549. The next prime is 18316601. The reversal of 18316561 is 16561381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16769025 + 1547536 = 4095^2 + 1244^2 .

It is an emirp because it is prime and its reverse (16561381) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18316561 - 2¹³ = 18308369 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18316061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9158280 + 9158281.

It is an arithmetic number, because the mean of its divisors is an integer number (9158281).

Almost surely, 2^18316561 is an apocalyptic number.

It is an amenable number.

18316561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18316561 is an equidigital number, since it uses as much as digits as its factorization.

18316561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 18316561 is about 4279.7851581592. The cubic root of 18316561 is about 263.6015616908.

The spelling of 18316561 in words is "eighteen million, three hundred sixteen thousand, five hundred sixty-one".