19889128121 has 8 divisors (see below), whose sum is σ = 21091941864. Its totient is φ = 18689966080.

The previous prime is 19889128117. The next prime is 19889128177. The reversal of 19889128121 is 12182198891.

It can be written as a sum of positive squares in 4 ways, for example, as 5576355625 + 14312772496 = 74675^2 + 119636^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19889128121 - 2² = 19889128117 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19889128121.

It is not an unprimeable number, because it can be changed into a prime (19889128621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 901700 + ... + 923493.

It is an arithmetic number, because the mean of its divisors is an integer number (2636492733).

Almost surely, 2^19889128121 is an apocalyptic number.

It is an amenable number.

19889128121 is a deficient number, since it is larger than the sum of its proper divisors (1202813743).

19889128121 is a wasteful number, since it uses less digits than its factorization.

19889128121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1825851.

The product of its digits is 165888, while the sum is 50.

The spelling of 19889128121 in words is "nineteen billion, eight hundred eighty-nine million, one hundred twenty-eight thousand, one hundred twenty-one".