18991891106 has 4 divisors (see below), whose sum is σ = 28487836662. Its totient is φ = 9495945552.

The previous prime is 18991891103. The next prime is 18991891117. The reversal of 18991891106 is 60119819981.

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

It can be written as a sum of positive squares in only one way, i.e., 13099947025 + 5891944081 = 114455^2 + 76759^2 .

It is not an unprimeable number, because it can be changed into a prime (18991891103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4747972775 + ... + 4747972778.

Almost surely, 2^18991891106 is an apocalyptic number.

18991891106 is a deficient number, since it is larger than the sum of its proper divisors (9495945556).

18991891106 is an equidigital number, since it uses as much as digits as its factorization.

18991891106 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9495945555.

The product of its (nonzero) digits is 279936, while the sum is 53.

The spelling of 18991891106 in words is "eighteen billion, nine hundred ninety-one million, eight hundred ninety-one thousand, one hundred six".