18549494581 has 2 divisors, whose sum is σ = 18549494582. Its totient is φ = 18549494580.

The previous prime is 18549494573. The next prime is 18549494599.

18549494581 is nontrivially palindromic in base 10.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17744637681 + 804856900 = 133209^2 + 28370^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 18549494581 - 2³ = 18549494573 is a prime.

It is a super-2 number, since 2×18549494581² (a number of 21 digits) contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18549494081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9274747290 + 9274747291.

It is an arithmetic number, because the mean of its divisors is an integer number (9274747291).

Almost surely, 2^18549494581 is an apocalyptic number.

It is an amenable number.

18549494581 is a deficient number, since it is larger than the sum of its proper divisors (1).

18549494581 is an equidigital number, since it uses as much as digits as its factorization.

18549494581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8294400, while the sum is 58.

The spelling of 18549494581 in words is "eighteen billion, five hundred forty-nine million, four hundred ninety-four thousand, five hundred eighty-one".