19918481991 has 4 divisors (see below), whose sum is σ = 26557975992. Its totient is φ = 13278987992.

The previous prime is 19918481971. The next prime is 19918482019.

19918481991 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 19918481991 - 2⁶ = 19918481927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19918481911) 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 3 ways as a sum of consecutive naturals, for example, 3319746996 + ... + 3319747001.

It is an arithmetic number, because the mean of its divisors is an integer number (6639493998).

Almost surely, 2^19918481991 is an apocalyptic number.

19918481991 is a deficient number, since it is larger than the sum of its proper divisors (6639494001).

19918481991 is an equidigital number, since it uses as much as digits as its factorization.

19918481991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6639494000.

The product of its digits is 1679616, while the sum is 60.

The spelling of 19918481991 in words is "nineteen billion, nine hundred eighteen million, four hundred eighty-one thousand, nine hundred ninety-one".