18911999905 has 8 divisors (see below), whose sum is σ = 22705466472. Its totient is φ = 15122222208.

The previous prime is 18911999839. The next prime is 18911999927. The reversal of 18911999905 is 50999911981.

It can be written as a sum of positive squares in 4 ways, for example, as 4353888256 + 14558111649 = 65984^2 + 120657^2 .

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 18911999905 - 2¹³ = 18911991713 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 910924 + ... + 931453.

It is an arithmetic number, because the mean of its divisors is an integer number (2838183309).

Almost surely, 2^18911999905 is an apocalyptic number.

It is an amenable number.

18911999905 is a deficient number, since it is larger than the sum of its proper divisors (3793466567).

18911999905 is a wasteful number, since it uses less digits than its factorization.

18911999905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1844435.

The product of its (nonzero) digits is 2361960, while the sum is 61.

The spelling of 18911999905 in words is "eighteen billion, nine hundred eleven million, nine hundred ninety-nine thousand, nine hundred five".