18921265309 has 4 divisors (see below), whose sum is σ = 18989573404. Its totient is φ = 18852957216.

The previous prime is 18921265301. The next prime is 18921265331. The reversal of 18921265309 is 90356212981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90356212981 = 10709 ⋅8437409.

It can be written as a sum of positive squares in 2 ways, for example, as 9330980409 + 9590284900 = 96597^2 + 97930^2 .

It is a cyclic number.

It is not a de Polignac number, because 18921265309 - 2³ = 18921265301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18921265301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34153632 + ... + 34154185.

It is an arithmetic number, because the mean of its divisors is an integer number (4747393351).

Almost surely, 2^18921265309 is an apocalyptic number.

It is an amenable number.

18921265309 is a deficient number, since it is larger than the sum of its proper divisors (68308095).

18921265309 is an equidigital number, since it uses as much as digits as its factorization.

18921265309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68308094.

The product of its (nonzero) digits is 233280, while the sum is 46.

The spelling of 18921265309 in words is "eighteen billion, nine hundred twenty-one million, two hundred sixty-five thousand, three hundred nine".