19491521805 has 64 divisors (see below), whose sum is σ = 39624499200. Its totient is φ = 8905308480.

The previous prime is 19491521783. The next prime is 19491521821. The reversal of 19491521805 is 50812519491.

19491521805 is a `hidden beast` number, since 1 + 9 + 49 + 1 + 521 + 80 + 5 = 666.

It is not a de Polignac number, because 19491521805 - 2⁷ = 19491521677 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2008956 + ... + 2018634.

It is an arithmetic number, because the mean of its divisors is an integer number (619132800).

Almost surely, 2^19491521805 is an apocalyptic number.

19491521805 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

19491521805 is an abundant number, since it is smaller than the sum of its proper divisors (20132977395).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19491521805 is a wasteful number, since it uses less digits than its factorization.

19491521805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11831 (or 11825 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 45.

The spelling of 19491521805 in words is "nineteen billion, four hundred ninety-one million, five hundred twenty-one thousand, eight hundred five".