18544166521 has 2 divisors, whose sum is σ = 18544166522. Its totient is φ = 18544166520.

The previous prime is 18544166483. The next prime is 18544166527. The reversal of 18544166521 is 12566144581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15015806521 + 3528360000 = 122539^2 + 59400^2 .

It is an emirp because it is prime and its reverse (12566144581) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18544166521 - 2¹⁹ = 18543642233 is a prime.

It is a super-2 number, since 2×18544166521² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18544166527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9272083260 + 9272083261.

It is an arithmetic number, because the mean of its divisors is an integer number (9272083261).

Almost surely, 2^18544166521 is an apocalyptic number.

It is an amenable number.

18544166521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18544166521 is an equidigital number, since it uses as much as digits as its factorization.

18544166521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 230400, while the sum is 43.

The spelling of 18544166521 in words is "eighteen billion, five hundred forty-four million, one hundred sixty-six thousand, five hundred twenty-one".