17971809821 has 8 divisors (see below), whose sum is σ = 20958379200. Its totient is φ = 15404408124.

The previous prime is 17971809809. The next prime is 17971809829. The reversal of 17971809821 is 12890817971.

It is not a de Polignac number, because 17971809821 - 2³⁰ = 16898067997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (17971809829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26197631 + ... + 26198316.

It is an arithmetic number, because the mean of its divisors is an integer number (2619797400).

Almost surely, 2^17971809821 is an apocalyptic number.

It is an amenable number.

17971809821 is a deficient number, since it is larger than the sum of its proper divisors (2986569379).

17971809821 is an frugal number, since it uses more digits than its factorization.

17971809821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52395968 (or 52395954 counting only the distinct ones).

The product of its (nonzero) digits is 508032, while the sum is 53.

The spelling of 17971809821 in words is "seventeen billion, nine hundred seventy-one million, eight hundred nine thousand, eight hundred twenty-one".