18531521791 has 2 divisors, whose sum is σ = 18531521792. Its totient is φ = 18531521790.

The previous prime is 18531521777. The next prime is 18531521821. The reversal of 18531521791 is 19712513581.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18531521791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18531521711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9265760895 + 9265760896.

It is an arithmetic number, because the mean of its divisors is an integer number (9265760896).

Almost surely, 2^18531521791 is an apocalyptic number.

18531521791 is a deficient number, since it is larger than the sum of its proper divisors (1).

18531521791 is an equidigital number, since it uses as much as digits as its factorization.

18531521791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75600, while the sum is 43.

The spelling of 18531521791 in words is "eighteen billion, five hundred thirty-one million, five hundred twenty-one thousand, seven hundred ninety-one".