999809709181 has 2 divisors, whose sum is σ = 999809709182. Its totient is φ = 999809709180.

The previous prime is 999809709169. The next prime is 999809709203. The reversal of 999809709181 is 181907908999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 499912632025 + 499897077156 = 707045^2 + 707034^2 .

It is an emirp because it is prime and its reverse (181907908999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999809709181 - 2⁹ = 999809708669 is a prime.

It is a super-2 number, since 2×999809709181² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 999809709181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999809709121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499904854590 + 499904854591.

It is an arithmetic number, because the mean of its divisors is an integer number (499904854591).

Almost surely, 2^999809709181 is an apocalyptic number.

It is an amenable number.

999809709181 is a deficient number, since it is larger than the sum of its proper divisors (1).

999809709181 is an equidigital number, since it uses as much as digits as its factorization.

999809709181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26453952, while the sum is 70.

The spelling of 999809709181 in words is "nine hundred ninety-nine billion, eight hundred nine million, seven hundred nine thousand, one hundred eighty-one".