18191930121 has 18 divisors (see below), whose sum is σ = 26848247322. Its totient is φ = 11869898880.

The previous prime is 18191930089. The next prime is 18191930137. The reversal of 18191930121 is 12103919181.

It can be written as a sum of positive squares in only one way, i.e., 15960784896 + 2231145225 = 126336^2 + 47235^2 .

It is not a de Polignac number, because 18191930121 - 2⁵ = 18191930089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18191930191) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 437640 + ... + 477401.

Almost surely, 2^18191930121 is an apocalyptic number.

It is an amenable number.

18191930121 is a deficient number, since it is larger than the sum of its proper divisors (8656317201).

18191930121 is an equidigital number, since it uses as much as digits as its factorization.

18191930121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 915141 (or 915091 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 36.

The spelling of 18191930121 in words is "eighteen billion, one hundred ninety-one million, nine hundred thirty thousand, one hundred twenty-one".