18811372781 has 2 divisors, whose sum is σ = 18811372782. Its totient is φ = 18811372780.

The previous prime is 18811372759. The next prime is 18811372843. The reversal of 18811372781 is 18727311881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10293928681 + 8517444100 = 101459^2 + 92290^2 .

It is a cyclic number.

It is not a de Polignac number, because 18811372781 - 2⁶ = 18811372717 is a prime.

It is a super-2 number, since 2×18811372781² (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 (18811372711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9405686390 + 9405686391.

It is an arithmetic number, because the mean of its divisors is an integer number (9405686391).

Almost surely, 2^18811372781 is an apocalyptic number.

It is an amenable number.

18811372781 is a deficient number, since it is larger than the sum of its proper divisors (1).

18811372781 is an equidigital number, since it uses as much as digits as its factorization.

18811372781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 150528, while the sum is 47.

The spelling of 18811372781 in words is "eighteen billion, eight hundred eleven million, three hundred seventy-two thousand, seven hundred eighty-one".