18690081521 has 2 divisors, whose sum is σ = 18690081522. Its totient is φ = 18690081520.

The previous prime is 18690081511. The next prime is 18690081563. The reversal of 18690081521 is 12518009681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17203207921 + 1486873600 = 131161^2 + 38560^2 .

It is an emirp because it is prime and its reverse (12518009681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18690081521 - 2⁶ = 18690081457 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (18690081511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9345040760 + 9345040761.

It is an arithmetic number, because the mean of its divisors is an integer number (9345040761).

Almost surely, 2^18690081521 is an apocalyptic number.

It is an amenable number.

18690081521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18690081521 is an equidigital number, since it uses as much as digits as its factorization.

18690081521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 41.

The spelling of 18690081521 in words is "eighteen billion, six hundred ninety million, eighty-one thousand, five hundred twenty-one".