18544043521 has 2 divisors, whose sum is σ = 18544043522. Its totient is φ = 18544043520.

The previous prime is 18544043501. The next prime is 18544043563. The reversal of 18544043521 is 12534044581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14117004225 + 4427039296 = 118815^2 + 66536^2 .

It is a cyclic number.

It is not a de Polignac number, because 18544043521 - 2⁷ = 18544043393 is a prime.

It is not a weakly prime, because it can be changed into another prime (18544043501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9272021760 + 9272021761.

It is an arithmetic number, because the mean of its divisors is an integer number (9272021761).

Almost surely, 2^18544043521 is an apocalyptic number.

It is an amenable number.

18544043521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18544043521 is an equidigital number, since it uses as much as digits as its factorization.

18544043521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 76800, while the sum is 37.

The spelling of 18544043521 in words is "eighteen billion, five hundred forty-four million, forty-three thousand, five hundred twenty-one".