18972920821 has 8 divisors (see below), whose sum is σ = 19630801080. Its totient is φ = 18315283392.

The previous prime is 18972920789. The next prime is 18972920851. The reversal of 18972920821 is 12802927981.

It can be written as a sum of positive squares in 4 ways, for example, as 1224020196 + 17748900625 = 34986^2 + 133225^2 .

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 18972920821 - 2⁵ = 18972920789 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 (18972920851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 106071 + ... + 221803.

It is an arithmetic number, because the mean of its divisors is an integer number (2453850135).

Almost surely, 2^18972920821 is an apocalyptic number.

It is an amenable number.

18972920821 is a deficient number, since it is larger than the sum of its proper divisors (657880259).

18972920821 is a wasteful number, since it uses less digits than its factorization.

18972920821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121415.

The product of its (nonzero) digits is 290304, while the sum is 49.

The spelling of 18972920821 in words is "eighteen billion, nine hundred seventy-two million, nine hundred twenty thousand, eight hundred twenty-one".