18716561 has 8 divisors (see below), whose sum is σ = 19329384. Its totient is φ = 18109440.

The previous prime is 18716557. The next prime is 18716597. The reversal of 18716561 is 16561781.

It can be written as a sum of positive squares in 4 ways, for example, as 7054336 + 11662225 = 2656^2 + 3415^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18716561 - 2² = 18716557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18716531) 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 in 7 ways as a sum of consecutive naturals, for example, 5831 + ... + 8451.

It is an arithmetic number, because the mean of its divisors is an integer number (2416173).

Almost surely, 2^18716561 is an apocalyptic number.

It is an amenable number.

18716561 is a deficient number, since it is larger than the sum of its proper divisors (612823).

18716561 is a wasteful number, since it uses less digits than its factorization.

18716561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2851.

The product of its digits is 10080, while the sum is 35.

The square root of 18716561 is about 4326.2640927248. The cubic root of 18716561 is about 265.5066183626.

The spelling of 18716561 in words is "eighteen million, seven hundred sixteen thousand, five hundred sixty-one".