19121989121 has 4 divisors (see below), whose sum is σ = 19183082052. Its totient is φ = 19060896192.

The previous prime is 19121989111. The next prime is 19121989157. The reversal of 19121989121 is 12198912191.

It is a happy number.

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 5046539521 + 14075449600 = 71039^2 + 118640^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19121989121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19121989111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30545996 + ... + 30546621.

It is an arithmetic number, because the mean of its divisors is an integer number (4795770513).

Almost surely, 2^19121989121 is an apocalyptic number.

It is an amenable number.

19121989121 is a deficient number, since it is larger than the sum of its proper divisors (61092931).

19121989121 is an equidigital number, since it uses as much as digits as its factorization.

19121989121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61092930.

The product of its digits is 23328, while the sum is 44.

The spelling of 19121989121 in words is "nineteen billion, one hundred twenty-one million, nine hundred eighty-nine thousand, one hundred twenty-one".