18375491021 has 4 divisors (see below), whose sum is σ = 18379945500. Its totient is φ = 18371036544.

The previous prime is 18375490997. The next prime is 18375491053. The reversal of 18375491021 is 12019457381.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12019457381 = 8219 ⋅1462399.

It can be written as a sum of positive squares in 2 ways, for example, as 12273537796 + 6101953225 = 110786^2 + 78115^2 .

It is a cyclic number.

It is not a de Polignac number, because 18375491021 - 2³⁰ = 17301749197 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18375491021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18375491621) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2221046 + ... + 2229303.

It is an arithmetic number, because the mean of its divisors is an integer number (4594986375).

Almost surely, 2^18375491021 is an apocalyptic number.

It is an amenable number.

18375491021 is a deficient number, since it is larger than the sum of its proper divisors (4454479).

18375491021 is an equidigital number, since it uses as much as digits as its factorization.

18375491021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4454478.

The product of its (nonzero) digits is 60480, while the sum is 41.

The spelling of 18375491021 in words is "eighteen billion, three hundred seventy-five million, four hundred ninety-one thousand, twenty-one".