18501840521 has 4 divisors (see below), whose sum is σ = 18805149444. Its totient is φ = 18198531600.

The previous prime is 18501840509. The next prime is 18501840551. The reversal of 18501840521 is 12504810581.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1219057225 + 17282783296 = 34915^2 + 131464^2 .

It is a cyclic number.

It is not a de Polignac number, because 18501840521 - 2¹⁰ = 18501839497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18501840551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 151654370 + ... + 151654491.

It is an arithmetic number, because the mean of its divisors is an integer number (4701287361).

Almost surely, 2^18501840521 is an apocalyptic number.

It is an amenable number.

18501840521 is a deficient number, since it is larger than the sum of its proper divisors (303308923).

18501840521 is an equidigital number, since it uses as much as digits as its factorization.

18501840521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 303308922.

The product of its (nonzero) digits is 12800, while the sum is 35.

The spelling of 18501840521 in words is "eighteen billion, five hundred one million, eight hundred forty thousand, five hundred twenty-one".