18910561 has 2 divisors, whose sum is σ = 18910562. Its totient is φ = 18910560.

The previous prime is 18910543. The next prime is 18910571. The reversal of 18910561 is 16501981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18792225 + 118336 = 4335^2 + 344^2 .

It is a cyclic number.

It is not a de Polignac number, because 18910561 - 2⁹ = 18910049 is a prime.

It is not a weakly prime, because it can be changed into another prime (18910501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9455280 + 9455281.

It is an arithmetic number, because the mean of its divisors is an integer number (9455281).

Almost surely, 2^18910561 is an apocalyptic number.

It is an amenable number.

18910561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18910561 is an equidigital number, since it uses as much as digits as its factorization.

18910561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 31.

The square root of 18910561 is about 4348.6274846209. The cubic root of 18910561 is about 266.4208058567.

The spelling of 18910561 in words is "eighteen million, nine hundred ten thousand, five hundred sixty-one".