181918200109 has 4 divisors (see below), whose sum is σ = 191492842240. Its totient is φ = 172343557980.

The previous prime is 181918200077. The next prime is 181918200151. The reversal of 181918200109 is 901002819181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 901002819181 = 349 ⋅2581669969.

It is a cyclic number.

It is not a de Polignac number, because 181918200109 - 2⁵ = 181918200077 is a prime.

It is a super-2 number, since 2×181918200109² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181918200179) 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, 4787321037 + ... + 4787321074.

It is an arithmetic number, because the mean of its divisors is an integer number (47873210560).

Almost surely, 2^181918200109 is an apocalyptic number.

181918200109 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

181918200109 is a deficient number, since it is larger than the sum of its proper divisors (9574642131).

181918200109 is an equidigital number, since it uses as much as digits as its factorization.

181918200109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9574642130.

The product of its (nonzero) digits is 10368, while the sum is 40.

The spelling of 181918200109 in words is "one hundred eighty-one billion, nine hundred eighteen million, two hundred thousand, one hundred nine".