19721250909 has 6 divisors (see below), whose sum is σ = 28486251326. Its totient is φ = 13147500600.

The previous prime is 19721250907. The next prime is 19721250919. The reversal of 19721250909 is 90905212791.

It can be written as a sum of positive squares in only one way, i.e., 19234916100 + 486334809 = 138690^2 + 22053^2 .

It is not a de Polignac number, because 19721250909 - 2¹ = 19721250907 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19721250907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1095625042 + ... + 1095625059.

Almost surely, 2^19721250909 is an apocalyptic number.

It is an amenable number.

19721250909 is a deficient number, since it is larger than the sum of its proper divisors (8765000417).

19721250909 is a wasteful number, since it uses less digits than its factorization.

19721250909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2191250107 (or 2191250104 counting only the distinct ones).

The product of its (nonzero) digits is 102060, while the sum is 45.

The spelling of 19721250909 in words is "nineteen billion, seven hundred twenty-one million, two hundred fifty thousand, nine hundred nine".