18508561981 has 16 divisors (see below), whose sum is σ = 23335377408. Its totient is φ = 14286960000.

The previous prime is 18508561969. The next prime is 18508561987. The reversal of 18508561981 is 18916580581.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 18508561981 - 2⁹ = 18508561469 is a prime.

It is a super-2 number, since 2×18508561981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18508561987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2476645 + ... + 2484106.

It is an arithmetic number, because the mean of its divisors is an integer number (1458461088).

Almost surely, 2^18508561981 is an apocalyptic number.

It is an amenable number.

18508561981 is a deficient number, since it is larger than the sum of its proper divisors (4826815427).

18508561981 is a wasteful number, since it uses less digits than its factorization.

18508561981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4960812.

The product of its (nonzero) digits is 691200, while the sum is 52.

The spelling of 18508561981 in words is "eighteen billion, five hundred eight million, five hundred sixty-one thousand, nine hundred eighty-one".