18121020109 has 2 divisors, whose sum is σ = 18121020110. Its totient is φ = 18121020108.

The previous prime is 18121020041. The next prime is 18121020121. The reversal of 18121020109 is 90102012181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13421917609 + 4699102500 = 115853^2 + 68550^2 .

It is an emirp because it is prime and its reverse (90102012181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18121020109 - 2⁹ = 18121019597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18121020179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9060510054 + 9060510055.

It is an arithmetic number, because the mean of its divisors is an integer number (9060510055).

Almost surely, 2^18121020109 is an apocalyptic number.

It is an amenable number.

18121020109 is a deficient number, since it is larger than the sum of its proper divisors (1).

18121020109 is an equidigital number, since it uses as much as digits as its factorization.

18121020109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 25.

The spelling of 18121020109 in words is "eighteen billion, one hundred twenty-one million, twenty thousand, one hundred nine".