18945911521 has 4 divisors (see below), whose sum is σ = 18949250992. Its totient is φ = 18942572052.

The previous prime is 18945911519. The next prime is 18945911539. The reversal of 18945911521 is 12511954981.

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 18945911521 - 2¹ = 18945911519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18945911561) 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, 1661211 + ... + 1672576.

It is an arithmetic number, because the mean of its divisors is an integer number (4737312748).

Almost surely, 2^18945911521 is an apocalyptic number.

It is an amenable number.

18945911521 is a deficient number, since it is larger than the sum of its proper divisors (3339471).

18945911521 is an equidigital number, since it uses as much as digits as its factorization.

18945911521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3339470.

The product of its digits is 129600, while the sum is 46.

The spelling of 18945911521 in words is "eighteen billion, nine hundred forty-five million, nine hundred eleven thousand, five hundred twenty-one".