191819191909 has 4 divisors (see below), whose sum is σ = 203102673804. Its totient is φ = 180535710016.

The previous prime is 191819191903. The next prime is 191819191931. The reversal of 191819191909 is 909191918191.

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 116919544225 + 74899647684 = 341935^2 + 273678^2 .

It is not a de Polignac number, because 191819191909 - 2³ = 191819191901 is a prime.

It is a super-3 number, since 3×191819191909³ (a number of 35 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191819191901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5641740922 + ... + 5641740955.

It is an arithmetic number, because the mean of its divisors is an integer number (50775668451).

Almost surely, 2^191819191909 is an apocalyptic number.

It is an amenable number.

191819191909 is a deficient number, since it is larger than the sum of its proper divisors (11283481895).

191819191909 is a wasteful number, since it uses less digits than its factorization.

191819191909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11283481894.

The product of its (nonzero) digits is 472392, while the sum is 58.

The spelling of 191819191909 in words is "one hundred ninety-one billion, eight hundred nineteen million, one hundred ninety-one thousand, nine hundred nine".