18889561 has 4 divisors (see below), whose sum is σ = 19350324. Its totient is φ = 18428800.

The previous prime is 18889531. The next prime is 18889583. The reversal of 18889561 is 16598881.

18889561 is nontrivially palindromic in base 15.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7733961 + 11155600 = 2781^2 + 3340^2 .

It is a cyclic number.

It is not a de Polignac number, because 18889561 - 2⁷ = 18889433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18889531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 230320 + ... + 230401.

It is an arithmetic number, because the mean of its divisors is an integer number (4837581).

Almost surely, 2^18889561 is an apocalyptic number.

It is an amenable number.

18889561 is a deficient number, since it is larger than the sum of its proper divisors (460763).

18889561 is an equidigital number, since it uses as much as digits as its factorization.

18889561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 460762.

The product of its digits is 138240, while the sum is 46.

The square root of 18889561 is about 4346.2122589676. The cubic root of 18889561 is about 266.3221500631.

It can be divided in two parts, 1888 and 9561, that added together give a square (11449 = 107²).

The spelling of 18889561 in words is "eighteen million, eight hundred eighty-nine thousand, five hundred sixty-one".