18191828209 has 4 divisors (see below), whose sum is σ = 18819132660. Its totient is φ = 17564523760.

The previous prime is 18191828191. The next prime is 18191828227. The reversal of 18191828209 is 90282819181.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (18191828191) and next prime (18191828227).

It can be written as a sum of positive squares in 2 ways, for example, as 12611290000 + 5580538209 = 112300^2 + 74703^2 .

It is a cyclic number.

It is not a de Polignac number, because 18191828209 - 2¹⁷ = 18191697137 is a prime.

It is a super-2 number, since 2×18191828209² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18191828609) 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, 313652182 + ... + 313652239.

It is an arithmetic number, because the mean of its divisors is an integer number (4704783165).

Almost surely, 2^18191828209 is an apocalyptic number.

It is an amenable number.

18191828209 is a deficient number, since it is larger than the sum of its proper divisors (627304451).

18191828209 is an equidigital number, since it uses as much as digits as its factorization.

18191828209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 627304450.

The product of its (nonzero) digits is 165888, while the sum is 49.

It can be divided in two parts, 18191 and 828209, that added together give a square (846400 = 920²).

The spelling of 18191828209 in words is "eighteen billion, one hundred ninety-one million, eight hundred twenty-eight thousand, two hundred nine".