18918920861 has 2 divisors, whose sum is σ = 18918920862. Its totient is φ = 18918920860.

The previous prime is 18918920789. The next prime is 18918920893. The reversal of 18918920861 is 16802981981.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18822193636 + 96727225 = 137194^2 + 9835^2 .

It is a cyclic number.

It is not a de Polignac number, because 18918920861 - 2²⁶ = 18851811997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18918926861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9459460430 + 9459460431.

It is an arithmetic number, because the mean of its divisors is an integer number (9459460431).

Almost surely, 2^18918920861 is an apocalyptic number.

It is an amenable number.

18918920861 is a deficient number, since it is larger than the sum of its proper divisors (1).

18918920861 is an equidigital number, since it uses as much as digits as its factorization.

18918920861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 497664, while the sum is 53.

The spelling of 18918920861 in words is "eighteen billion, nine hundred eighteen million, nine hundred twenty thousand, eight hundred sixty-one".