18612633581 has 2 divisors, whose sum is σ = 18612633582. Its totient is φ = 18612633580.

The previous prime is 18612633563. The next prime is 18612633659. The reversal of 18612633581 is 18533621681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12967515625 + 5645117956 = 113875^2 + 75134^2 .

It is an emirp because it is prime and its reverse (18533621681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18612633581 - 2¹⁰ = 18612632557 is a prime.

It is a super-2 number, since 2×18612633581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18612633541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9306316790 + 9306316791.

It is an arithmetic number, because the mean of its divisors is an integer number (9306316791).

Almost surely, 2^18612633581 is an apocalyptic number.

It is an amenable number.

18612633581 is a deficient number, since it is larger than the sum of its proper divisors (1).

18612633581 is an equidigital number, since it uses as much as digits as its factorization.

18612633581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 207360, while the sum is 44.

The spelling of 18612633581 in words is "eighteen billion, six hundred twelve million, six hundred thirty-three thousand, five hundred eighty-one".