19910056609 has 9 divisors (see below), whose sum is σ = 20065766707. Its totient is φ = 19755548824.

The previous prime is 19910056603. The next prime is 19910056619. The reversal of 19910056609 is 90665001991.

The square root of 19910056609 is 141103.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 2332600209 + 17577456400 = 48297^2 + 132580^2 .

It is not a de Polignac number, because 19910056609 - 2⁵ = 19910056577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19910056603) 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 8 ways as a sum of consecutive naturals, for example, 21023874 + ... + 21024820.

Almost surely, 2^19910056609 is an apocalyptic number.

19910056609 is the 141103-rd square number.

19910056609 is the 70552-nd centered octagonal number.

It is an amenable number.

19910056609 is a deficient number, since it is larger than the sum of its proper divisors (155710098).

19910056609 is an frugal number, since it uses more digits than its factorization.

19910056609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2192 (or 1096 counting only the distinct ones).

The product of its (nonzero) digits is 131220, while the sum is 46.

The spelling of 19910056609 in words is "nineteen billion, nine hundred ten million, fifty-six thousand, six hundred nine".