18720420109 has 2 divisors, whose sum is σ = 18720420110. Its totient is φ = 18720420108.

The previous prime is 18720420071. The next prime is 18720420127. The reversal of 18720420109 is 90102402781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10868688009 + 7851732100 = 104253^2 + 88610^2 .

It is an emirp because it is prime and its reverse (90102402781) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18720420109 - 2⁷ = 18720419981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18720420139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9360210054 + 9360210055.

It is an arithmetic number, because the mean of its divisors is an integer number (9360210055).

Almost surely, 2^18720420109 is an apocalyptic number.

It is an amenable number.

18720420109 is a deficient number, since it is larger than the sum of its proper divisors (1).

18720420109 is an equidigital number, since it uses as much as digits as its factorization.

18720420109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 34.

The spelling of 18720420109 in words is "eighteen billion, seven hundred twenty million, four hundred twenty thousand, one hundred nine".