18521431937993 has 2 divisors, whose sum is σ = 18521431937994. Its totient is φ = 18521431937992.

The previous prime is 18521431937977. The next prime is 18521431938011. The reversal of 18521431937993 is 39973913412581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14500155720649 + 4021276217344 = 3807907^2 + 2005312^2 .

It is a cyclic number.

It is not a de Polignac number, because 18521431937993 - 2⁴ = 18521431937977 is a prime.

It is not a weakly prime, because it can be changed into another prime (18521431937903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9260715968996 + 9260715968997.

It is an arithmetic number, because the mean of its divisors is an integer number (9260715968997).

Almost surely, 2^{18521431937993} is an apocalyptic number.

It is an amenable number.

18521431937993 is a deficient number, since it is larger than the sum of its proper divisors (1).

18521431937993 is an equidigital number, since it uses as much as digits as its factorization.

18521431937993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 44089920, while the sum is 65.

The spelling of 18521431937993 in words is "eighteen trillion, five hundred twenty-one billion, four hundred thirty-one million, nine hundred thirty-seven thousand, nine hundred ninety-three".