18156961909 has 4 divisors (see below), whose sum is σ = 18157479340. Its totient is φ = 18156444480.

The previous prime is 18156961897. The next prime is 18156961913. The reversal of 18156961909 is 90916965181.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15780886884 + 2376075025 = 125622^2 + 48745^2 .

It is a cyclic number.

It is not a de Polignac number, because 18156961909 - 2¹¹ = 18156959861 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18156961909.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18156961969) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 201924 + ... + 277645.

It is an arithmetic number, because the mean of its divisors is an integer number (4539369835).

Almost surely, 2^18156961909 is an apocalyptic number.

It is an amenable number.

18156961909 is a deficient number, since it is larger than the sum of its proper divisors (517431).

18156961909 is an equidigital number, since it uses as much as digits as its factorization.

18156961909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 517430.

The product of its (nonzero) digits is 1049760, while the sum is 55.

The spelling of 18156961909 in words is "eighteen billion, one hundred fifty-six million, nine hundred sixty-one thousand, nine hundred nine".