18193807821 has 16 divisors (see below), whose sum is σ = 27738854528. Its totient is φ = 10390852800.

The previous prime is 18193807777. The next prime is 18193807889. The reversal of 18193807821 is 12870839181.

It is a happy number.

It is not a de Polignac number, because 18193807821 - 2⁷ = 18193807693 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18193407821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 193690 + ... + 271851.

It is an arithmetic number, because the mean of its divisors is an integer number (1733678408).

Almost surely, 2^18193807821 is an apocalyptic number.

It is an amenable number.

18193807821 is a deficient number, since it is larger than the sum of its proper divisors (9545046707).

18193807821 is a wasteful number, since it uses less digits than its factorization.

18193807821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 467412.

The product of its (nonzero) digits is 193536, while the sum is 48.

The spelling of 18193807821 in words is "eighteen billion, one hundred ninety-three million, eight hundred seven thousand, eight hundred twenty-one".