18978487981 has 2 divisors, whose sum is σ = 18978487982. Its totient is φ = 18978487980.

The previous prime is 18978487961. The next prime is 18978488117.

18978487981 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., 18972583081 + 5904900 = 137741^2 + 2430^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 18978487981 - 2⁵ = 18978487949 is a prime.

It is a super-2 number, since 2×18978487981² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 18978487981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18978487961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9489243990 + 9489243991.

It is an arithmetic number, because the mean of its divisors is an integer number (9489243991).

Almost surely, 2^18978487981 is an apocalyptic number.

It is an amenable number.

18978487981 is a deficient number, since it is larger than the sum of its proper divisors (1).

18978487981 is an equidigital number, since it uses as much as digits as its factorization.

18978487981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 65028096, while the sum is 70.

The spelling of 18978487981 in words is "eighteen billion, nine hundred seventy-eight million, four hundred eighty-seven thousand, nine hundred eighty-one".