999634087518821 has 2 divisors, whose sum is σ = 999634087518822. Its totient is φ = 999634087518820.

The previous prime is 999634087518811. The next prime is 999634087518823. The reversal of 999634087518821 is 128815780436999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 504290574652225 + 495343512866596 = 22456415^2 + 22256314^2 .

It is an emirp because it is prime and its reverse (128815780436999) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999634087518821 is a prime.

Together with 999634087518823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999634087518823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499817043759410 + 499817043759411.

It is an arithmetic number, because the mean of its divisors is an integer number (499817043759411).

It is a 2-persistent number, because it is pandigital, and so is 2⋅999634087518821 = 1999268175037642, but 3⋅999634087518821 = 2998902262556463 is not.

Almost surely, 2^{999634087518821} is an apocalyptic number.

It is an amenable number.

999634087518821 is a deficient number, since it is larger than the sum of its proper divisors (1).

999634087518821 is an equidigital number, since it uses as much as digits as its factorization.

999634087518821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1881169920, while the sum is 80.

The spelling of 999634087518821 in words is "nine hundred ninety-nine trillion, six hundred thirty-four billion, eighty-seven million, five hundred eighteen thousand, eight hundred twenty-one".