18071988821 has 2 divisors, whose sum is σ = 18071988822. Its totient is φ = 18071988820.

The previous prime is 18071988793. The next prime is 18071988853. The reversal of 18071988821 is 12888917081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13756944100 + 4315044721 = 117290^2 + 65689^2 .

It is a cyclic number.

It is not a de Polignac number, because 18071988821 - 2¹⁸ = 18071726677 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18071988521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9035994410 + 9035994411.

It is an arithmetic number, because the mean of its divisors is an integer number (9035994411).

Almost surely, 2^18071988821 is an apocalyptic number.

It is an amenable number.

18071988821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18071988821 is an equidigital number, since it uses as much as digits as its factorization.

18071988821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 516096, while the sum is 53.

The spelling of 18071988821 in words is "eighteen billion, seventy-one million, nine hundred eighty-eight thousand, eight hundred twenty-one".