18521019521 has 4 divisors (see below), whose sum is σ = 18521330352. Its totient is φ = 18520708692.

The previous prime is 18521019511. The next prime is 18521019523. The reversal of 18521019521 is 12591012581.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18521019521 - 2⁶ = 18521019457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18521019523) 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, 34871 + ... + 195596.

It is an arithmetic number, because the mean of its divisors is an integer number (4630332588).

Almost surely, 2^18521019521 is an apocalyptic number.

It is an amenable number.

18521019521 is a deficient number, since it is larger than the sum of its proper divisors (310831).

18521019521 is an equidigital number, since it uses as much as digits as its factorization.

18521019521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310830.

The product of its (nonzero) digits is 7200, while the sum is 35.

The spelling of 18521019521 in words is "eighteen billion, five hundred twenty-one million, nineteen thousand, five hundred twenty-one".