18691909 has 2 divisors, whose sum is σ = 18691910. Its totient is φ = 18691908.

The previous prime is 18691889. The next prime is 18691927. The reversal of 18691909 is 90919681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18301284 + 390625 = 4278^2 + 625^2 .

It is a cyclic number.

It is not a de Polignac number, because 18691909 - 2⁹ = 18691397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18692909) 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, 9345954 + 9345955.

It is an arithmetic number, because the mean of its divisors is an integer number (9345955).

Almost surely, 2^18691909 is an apocalyptic number.

It is an amenable number.

18691909 is a deficient number, since it is larger than the sum of its proper divisors (1).

18691909 is an equidigital number, since it uses as much as digits as its factorization.

18691909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 34992, while the sum is 43.

The square root of 18691909 is about 4323.4140444792. The cubic root of 18691909 is about 265.3899989171.

It can be divided in two parts, 18691 and 909, that added together give a square (19600 = 140²).

The spelling of 18691909 in words is "eighteen million, six hundred ninety-one thousand, nine hundred nine".